ARARandand

THRTHR

ThyroidThyroid glandsglands•• The thyroid gland The thyroid gland isis a a stronglystrongly vascularizedvascularizedorganorgan

•• ItIt is located in the neck, in close approximation to the first partis located in the neck, in close approximation to the first part of the trachea. of the trachea.

•• In humans, the thyroid gland has a In humans, the thyroid gland has a "butterfly" shape, with two lateral lobes that "butterfly" shape, with two lateral lobes that are connected by a narrow section called the are connected by a narrow section called the isthmus. isthmus.

•• Most animals, however, have two separate Most animals, however, have two separate glands on either side of the trachea. glands on either side of the trachea.

•• Thyroid glands are brownishThyroid glands are brownish--red in color. red in color.

ThyroidThyroid glandsglands•• Thyroid epithelial cells Thyroid epithelial cells -- the cells responsible for synthesis of thyroid hormones the cells responsible for synthesis of thyroid hormones -- are are arranged in spheres called arranged in spheres called thyroid folliclesthyroid follicles. .

•• The follicle lumen is filled with a thickThe follicle lumen is filled with a thick colloid which predominantly containscolloid which predominantly containsthyroglobulinthyroglobulin . .

•• ThyroglobulinThyroglobulin is a highly is a highly glycosylatedglycosylatedprotein of two subunits, each of 330 protein of two subunits, each of 330 kDakDa. The. Thesubunit contains 115 tyrosine residues. This way, the thyroid glsubunit contains 115 tyrosine residues. This way, the thyroid gl and maintains a largeand maintains a largereservoir of potential hormone. reservoir of potential hormone.

•• Thyroid hormones are derivatives of the amino acid tyrosine bounThyroid hormones are derivatives of the amino acid tyrosine bound covalently to d covalently to iodine. The two principal thyroid hormones are: iodine. The two principal thyroid hormones are:

•• thyroxinethyroxine (known (known alsoalsoas as T4T4 or Lor L --3,5,3',5'3,5,3',5'--tetraiodothyroninetetraiodothyronine; major form ; major form releasedreleasedfromfrom thethe glandgland) )

•• triiodottriiodot hhyronineyronine ((T3T3 or Lor L --3,5,3'3,5,3'--triiodothyronine). triiodothyronine).

•• Although both T3 and T4 are important for normal growth and deveAlthough both T3 and T4 are important for normal growth and development and lopment and energy metabolism,energy metabolism,T3T3 isis ~10~10timestimes more active more active ligand ligand ofof THR THR than T4than T4..

ThyroidThyroid hormoneshormones

TThyroidhyroid hormones are basically two hormones are basically two tyrosinestyrosineslinked together with the critical addition linked together with the critical addition of iodine at three or four positions on the aromatic rings. of iodine at three or four positions on the aromatic rings.

Physiologic Physiologic eeffectsffects of of tthyroidhyroid hhormonesormones

•• It is likely that all cells in the body are targets for It is likely that all cells in the body are targets for thyroid hormones. thyroid hormones.

•• TThyroidhyroid hormones have profound effects on hormones have profound effects on many "big time" physiologic processes, such as many "big time" physiologic processes, such as development, growth and metabolism. development, growth and metabolism.

Metabolism: Metabolism:

•• Thyroid hormones stimulate diverse metabolic Thyroid hormones stimulate diverse metabolic activities activities inin most tissues, leading to an increase in most tissues, leading to an increase in basal metabolic rate. basal metabolic rate.

•• One consequence of this activity is to increase One consequence of this activity is to increase body heat production, which seems to result, at body heat production, which seems to result, at least in part, from increased oxygen consumption least in part, from increased oxygen consumption and rates of ATP hydrolysis. and rates of ATP hydrolysis.

Mitochondrial ATP production in control (open bars) and hyperthyroid (filled bars) in rats.

heart liver soleus plantaris

Physiologic Physiologic eeffectsffects of of tthyroidhyroid hhormonesormones

Growth: Growth:

•• Thyroid hormones are clearly necessary for normal growth in chilThyroid hormones are clearly necessary for normal growth in chil dren and young dren and young animals, as evidenced by the growthanimals, as evidenced by the growth--retardation observed in thyroid deficiency. retardation observed in thyroid deficiency.

Development: Development:

•• A classical experiment in endocrinology was the demonstration thA classical experiment in endocrinology was the demonstration th at tadpoles deprived of at tadpoles deprived of thyroid hormone failed to undergo metamorphosis into frogs. thyroid hormone failed to undergo metamorphosis into frogs.

Rot-Nikcevic & Wassersug, J Exp Biol 2004.

Rana Rana temporariatemporaria XenopusXenopuslaevislaevis

healthy

lack of thyroid gland

Physiologic Physiologic eeffectsffects of of tthyroidhyroid hhormonesormones

Central nervous system:Central nervous system:

•• Both decreased and increased concentrations of Both decreased and increased concentrations of thyroid hormones lead to alterations in mental thyroid hormones lead to alterations in mental state. Too little thyroid hormone, and the state. Too little thyroid hormone, and the individual tends to feel mentally sluggish, while too individual tends to feel mentally sluggish, while too much induces anxiety and nervousness. much induces anxiety and nervousness.

•• Of critical importance in mammals is the fact Of critical importance in mammals is the fact that normal levels of thyroid hormone are essential that normal levels of thyroid hormone are essential to the development of the fetal and neonatal brain. to the development of the fetal and neonatal brain.

•• Congenital thyroid deficiency results in Congenital thyroid deficiency results in cretinism, whichcretinism, which includes dwarfism and mental includes dwarfism and mental retardation.retardation.

•• Mammalian thyroid hormone receptors are encoded by two genes, deMammalian thyroid hormone receptors are encoded by two genes, designated alpha and signated alpha and beta. beta.

•• TThe primary transcript for each gene can be alternatively splicedhe primary transcript for each gene can be alternatively spliced, generating different , generating different alpha and beta receptor alpha and beta receptor isoformsisoforms. .

•• Currently, four different thyroid hormone receptors are recognizCurrently, four different thyroid hormone receptors are recognized: alphaed: alpha--1, alpha1, alpha--2, 2, betabeta--1 and beta1 and beta--2. 2.

•• Most notably, theMost notably, thealphaalpha--22 isoformisoform has a unique has a unique carboxycarboxy--terminus andterminus and does not binddoes not bindT3.T3.

ThyroidThyroid hormonehormone receptor (THR) receptor (THR)

•• Thyroid hormone receptors can bind to a TRE as Thyroid hormone receptors can bind to a TRE as monomersmonomers, as, as homodimershomodimers or asor asheterodimersheterodimerswith the retinoid X receptor (RXR). with the retinoid X receptor (RXR).

•• The The heterodimerheterodimer affords the highest affinity binding, and is thought to represeaffords the highest affinity binding, and is thought to represent the nt the major functional formmajor functional form of the receptor. of the receptor.

•• The most stable binding occurs onThe most stable binding occurs onthe classical DR4 thyroid responsethe classical DR4 thyroid responseelement element (TRE)(TRE)..

•• Thyroid hormone receptors bind to TRE DNA regardless of whether Thyroid hormone receptors bind to TRE DNA regardless of whether they are occupied they are occupied by T3. However, the biological effects of TRE binding by the unoby T3. However, the biological effects of TRE binding by the unoccupied versus the ccupied versus the occupied receptor are dramatically different. occupied receptor are dramatically different.

•• In general, In general, binding of thyroid hormonebinding of thyroid hormone receptor alonereceptor alone to DNA leads toto DNA leads to repressionrepression of of transcription, whereas binding of the thyroid transcription, whereas binding of the thyroid hormonehormone--receptor complexreceptor complex leadsleads to to activatactivationion ofof transcription. transcription.

LigandLigand--free state:free state:

•• The The transactivationtransactivation domain of the T3domain of the T3--free receptor, as a free receptor, as a heterodimerheterodimer with RXR, with RXR, assumes a conformation that promotes interaction with a group ofassumes a conformation that promotes interaction with a group of transcriptional transcriptional corepressorcorepressormolecules. molecules.

•• A part of this A part of this corepressorcorepressorcomplex has complex has histonehistone deacetylasedeacetylaseactivity (HDAactivity (HDA CC), which is ), which is associated with formation of a compact, "turnedassociated with formation of a compact, "turned--off" conformation of chromatin. off" conformation of chromatin.

•• The net effect of recruiting these types ofThe net effect of recruiting these types oftranscription factors is transcription factors is to repress transcriptionto repress transcriptionfrom affected genes.from affected genes.

ModeMode ofof THR THR actionaction

ThyroidThyroid hormonehormone receptorreceptor

LigandLigand--boundbound state: state:

•• Binding of T3 to its receptor induces a conformational change inBinding of T3 to its receptor induces a conformational change in the receptor that the receptor that makes it incompetent to bind the makes it incompetent to bind the corepressorcorepressorcomplex, but competent to bind a group of complex, but competent to bind a group of coactivatorcoactivator proteins. proteins.

•• The The coactivatorcoactivator complex contains complex contains histonehistone transacetylasetransacetylase(HAT) activity, which imposes (HAT) activity, which imposes an open configuration on adjacent chromatin. an open configuration on adjacent chromatin.

•• The The coactivatorcoactivator complex associated with the complex associated with the T3T3--bound receptor functions to activate bound receptor functions to activate transcription from linked genes.transcription from linked genes.

•• TR TR cancanalsoalso transrepresstransrepressgenes in its genes in its ligandedligandedstate via inhibitingstate via inhibitingother transcription factors other transcription factors such as APsuch as AP--1.1.

HypothyroidismHypothyroidismCausesCauses::

•• Iodine deficiencyIodine deficiency

•• Primary thyroid disease Primary thyroid disease (e.g. (e.g. Hashimoto'sHashimoto's diseasedisease, ,

autoimmuneautoimmune diseasesdiseasesleadingleadingto to inflammationinflammation ))

HSHShealthyhealthy

HyperthyroidismHyperthyroidismCausesCauses::

•• TooToo high high secretion of thyroid hormonessecretion of thyroid hormones((less common than hypothyroidismless common than hypothyroidism)). .

•• Graves disease, an Graves disease, an autoautoimmune disease in which antibodies bind to and activate the immune disease in which antibodies bind to and activate the thyroidthyroid --stimulating hormone receptor, leading to continual stimulation ostimulating hormone receptor, leading to continual stimulation of thyroid hormone f thyroid hormone synthesis. synthesis.

•• ThyroidThyroid cancercancer..

•• Hamburger Hamburger thyroxicosisthyroxicosis ((rarerare ☺☺☺☺☺☺☺☺)). .

Exophthalmos

•• People, and presumably pets, that eat such hamburger can get dosPeople, and presumably pets, that eat such hamburger can get dose of thyroid hormone e of thyroid hormone sufficient to induce disease. sufficient to induce disease.

•• ItIt hashas beenbeen describeddescribed (1987) (1987) an outbreak of an outbreak of thyrotoxicosisthyrotoxicosis in Minnesota and South in Minnesota and South Dakota that was traced to thyroidDakota that was traced to thyroid--contaminated hamburger. A total of 121 cases were contaminated hamburger. A total of 121 cases were identified in identified in USA.USA.

•• The patients complained of sleeplessness, nervousness, headache,The patients complained of sleeplessness, nervousness, headache, fatiquefatique, excessive , excessive sweating and weight loss. sweating and weight loss.

Hamburger Hamburger thyroxicosisthyroxicosis•• Thyroid hormones are orally activeThyroid hormones are orally active, which means that , which means that consumption of thyroid gland tissue can cause consumption of thyroid gland tissue can cause thyrotoxicosisthyrotoxicosis, a , a type of hyperthyroidism. type of hyperthyroidism.

•• Several outbreaks of Several outbreaks of thyrotoxicosisthyrotoxicosis have been attributed to a have been attributed to a practice practice ((bannedbanned)), where meat in the neck region of slaughtered , where meat in the neck region of slaughtered animals is ground into hamburgeranimals is ground into hamburger. Because thyroid glands are . Because thyroid glands are reddish in color and located in the neck, it's not unusual to gereddish in color and located in the neck, it's not unusual to get t thyroid glands into hamburger or sausage. thyroid glands into hamburger or sausage.

Hamburger Hamburger thyroxicosisthyroxicosis•• SSerumerum concentrations of concentrations of thyroxinethyroxine and thyroidand thyroid--stimulating hormone in a volunteer stimulating hormone in a volunteer that consumed a that consumed a wellwell--cookedcooked, 227 g hamburger prepared from the contaminated meat. , 227 g hamburger prepared from the contaminated meat. Note how TSH levels were suppressed during the time when Note how TSH levels were suppressed during the time when thyroxinethyroxine (T4) (T4) concentrations were elevated. concentrations were elevated.

•• Mutations in the ligandMutations in the ligand--binding domain of Tbinding domain of THHR can lead to generalizedR can lead to generalizedresistance to resistance to thyroid hormones. thyroid hormones.

MutationsMutations inin THRTHR

•• Clinically, such individuals show a type of hypothyroidism charaClinically, such individuals show a type of hypothyroidism characterized by goiter, cterized by goiter, elevated serum concentrations of T3 and elevated serum concentrations of T3 and thyroxinethyroxine and normal or elevated serum and normal or elevated serum concentrations of TSH. concentrations of TSH.

Thyroid Thyroid hhormoneormone andand fetalfetal developmentdevelopment•• ThyThyroidroid hormones are critical for development of the fetal and neonatalhormones are critical for development of the fetal and neonatalbrain, as well as brain, as well as for many other aspects of fetal growth. for many other aspects of fetal growth. HypothyroidismHypothyroidism in either the mother or fetus in either the mother or fetus frequently results in fetal disease; in humans, this includesfrequently results in fetal disease; in humans, this includes a high incidence of mental a high incidence of mental retardationretardation . .

•• The fetus has two potential sources of thyroid hormones The fetus has two potential sources of thyroid hormones -- it's own thyroid and the it's own thyroid and the thyroid of it's mother. thyroid of it's mother.

•• Human fetuses acquire the Human fetuses acquire the ability to synthesize thyroid ability to synthesize thyroid hormones at 10 to 12 weeks of hormones at 10 to 12 weeks of gestation. gestation.

•• TThere is substantial transfer here is substantial transfer of maternal thyroid hormones of maternal thyroid hormones across the placenta.across the placenta.

•• Additionally, the placenta Additionally, the placenta contains contains deiodinasesdeiodinasesthat can that can convert T4 to T3. convert T4 to T3.

Thyroid Thyroid hhormoneormone andand fetalfetal brainbrain developmentdevelopment•• In 1888 the Clinical Society of London issued a report In 1888 the Clinical Society of London issued a report underlining the importance of normal thyroid functi on on underlining the importance of normal thyroid functi on on development of the brain. development of the brain.

•• TThyroidhyroid hormones appear to have their most profound effects hormones appear to have their most profound effects on the terminal stages of brain differentiation, including on the terminal stages of brain differentiation, including synaptogenesissynaptogenesis, growth of dendrites and axons, , growth of dendrites and axons, myelinationmyelination and and neuronal migration. neuronal migration.

•• TThe promoter of the he promoter of the myelin basic proteinmyelin basic protein gene is directly gene is directly responsive to thyroid hormones and responsive to thyroid hormones and contains contains thyroidthyroid hormone hormone response elementresponse element. .

AA fetal rat brain produced by in situ hybridization fetal rat brain produced by in situ hybridization with a probe for the rat thyroid hormone receptor. with a probe for the rat thyroid hormone receptor.

PurkinjePurkinjecellscellskeptkeptfor 14 for 14 daysdaysinin cultureculture inin thetheabsenceabsenceoror presencepresenceofof TH . TH . TH TH inducedinduceddramaticdramaticincreaseincreaseinin PurkinjePurkinjecellcell dendriticdendriticbranchingbranching. .

Thyroid Thyroid hhormoneormone andand fetalfetal developmentdevelopment

TThyroidhyroid deficiency states known to affect fetal development: deficiency states known to affect fetal development:

** Isolated maternal hypothyroidism:Isolated maternal hypothyroidism: MM aternalaternal hypothyroidism typically is not a hypothyroidism typically is not a significant cause of fetal disease because it usually is associasignificant cause of fetal disease because it usually is associated with infertility. When ted with infertility. When pregnancy does occur, there is increased risk of intrauterine fepregnancy does occur, there is increased risk of intrauterine fetal death and gestational tal death and gestational hypertension.hypertension.

* * SSubclinubcliniical hypothyroidismcal hypothyroidism:: mild maternal hypothyroidism, diagnosed only mild maternal hypothyroidism, diagnosed only retrospectively from banked serum, may adversely affect the feturetrospectively from banked serum, may adversely affect the fetus, leading in children to s, leading in children to such effects as slightly such effects as slightly lower performance on IQ testslower performance on IQ testsand difficulties with schoolwork. and difficulties with schoolwork. The most common cause of The most common cause of subclinicalsubclinical hypothyroidism is autoimmune disease, and it is hypothyroidism is autoimmune disease, and it is known that antiknown that anti--thyroid antibodies cross the human placenta.thyroid antibodies cross the human placenta.

* * Isolated fetal hypothyroidism:Isolated fetal hypothyroidism: failure of the fetal thyroid gland to produce adequate failure of the fetal thyroid gland to produce adequate amounts of thyroid hormone. Most children are amounts of thyroid hormone. Most children are normal at birthnormal at birth , because maternal , because maternal thyroid hormones are transported across the placenta during gestthyroid hormones are transported across the placenta during gestation. What is ation. What is absolutely critical is to identify and treat this condition veryabsolutely critical is to identify and treat this condition very shortly after birth. If shortly after birth. If notnot, the , the child will become permanently mentally and growth retarded child will become permanently mentally and growth retarded ((cretinismcretinism -- a marked a marked impairment of the capacity for abstract thoughtimpairment of the capacity for abstract thought, , withwith preservedpreserved vvegetativeegetative, personal, , personal, social functions and memory. social functions and memory. VeryVery oftenoften associatedassociatedwithwith deafnessdeafness).).

fewfew monthsmonths

thyroidthyroid hormonehormone replacementreplacement

Isolated fetal hypothyroidism:Isolated fetal hypothyroidism:

-- TheThe most most abundantlyabundantly synthetizedsynthetized ligand ligand ofof androgen androgen receptorsreceptors (7 mg/(7 mg/ddayay) ) isistestosterontestosteronee. . ItIt isis producedproduced by by thethe LeydigLeydig cellscells inin responseresponse to to luteinizingluteinizing hormonehormoneproducedproduced inin thethe pinealpineal glandgland..

AndrogAndrogeennss –– generalgeneralcharacteristicscharacteristics

Estrogens

Glucocorticoids

-- ProductionProduction ofof testosteronetestosteronechangeschangesperiodicallyperiodically withwith circadiancircadian andand seasonalseasonalpeakspeaks..

AndrogAndrogeennss –– generalgeneralcharacteristicscharacteristics

-- In In thethe targettarget cellscells testosteronetestosteroneisis changedchangedintointo 2 2 activeactive metabolitesmetabolites: :

* * dihydrotestosterondihydrotestosteronee (DHT)(DHT) ((enzymenzymee: 5: 5αααααααα--redureductasectase, , expressedexpressedinin 2 2 isoformsisoforms, I i II), I i II)* estradiol* estradiol ((enzymenzymee: : aromataaromatasese))

AndrogAndrogeennss –– generalgeneralcharacteristicscharacteristics

Mouse Leydig cell in primary culture.ActinActin fibersfibersstainedstainedwithwith labelledlabelled--phalloidinphalloidin (red), DNA ((red), DNA (blueblue). ).

aromatase

Respective roles of testosterone (T) anddihydrotestosterone (DHT) in sex differentiation

55αααααααα--redureducctatase se deficiencydeficiency::* * ItIt maymay leadlead to to malemale pseudohermaphroditismpseudohermaphroditism, , becausebecausetherethere isis impairedimpaired productionproduction ofof

DHT DHT fromfrom testosteronetestosterone((testosteronetestosteroneproductionproduction isis normalnormal). ).

* * TypeType ofof developmentdevelopment((appearenceappearence, , behaviorbehavior) ) isis typicaltypical for men. for men.

* * As As thethe androgenandrogen receptorsreceptors functionfunction normallynormally , , testosteronetestosteroneisis ableable to bind to to bind to themthem andand provideprovidenormalnormal sexualsexual functionfunction withwith adequateadequate libido, libido, erectileerectile functionfunction, , andand spermatogenesisspermatogenesis,, but but dihydrotestosteronedihydrotestosterone productionproduction isis seversevereelylylimitedlimited inin prostateprostate andand scalpscalp, , withwith lowlowcirculatingcirculating levelslevels. .

* * TheThe affectedaffected individualsindividuals havehaveno no facialfacial oror body body hairhair , do not, do not show show temporaltemporal hairlinehairline recessionrecessionoror vertexvertex baldingbalding, , havehavenormalnormal scalpscalphairhair , , aandnd theirtheir prostateprostate glandgland remainremainss smallsmall ((thusthus, , theythey areare infertileinfertile ))..

High High expressionexpression ofof 5a 5a reductasereductase

non-balding scalp

balding scalp

-- AR was AR was clonedcloned inin 1988. 1988. ThereThere areare isoformsisoforms ofof ARAR (98.4(98.4--100 100 kDakDa). ).

-- DifferentDifferent sizessizesofof AR AR proteinsproteins resultresult fromfrom thethe polymorphismpolymorphism ofof glycineglycine--reachreach sequencesequence(GGC) (GGC) oror glutamineglutamine--reachreach sequencesequence(GAC) (GAC) atat thethe NN--terminusterminus. .

-- FunctionFunction ofof thesethese repetitionrepetition isis not not fullyfully recognizedrecognized, but , but elongatedelongated GAC fragment GAC fragment decreasesdecreasestranscriptionaltranscriptional activityactivity ofof AR proteinAR protein ..

-- NN--terminal terminal repeatsrepeats ofof GGAAC C areare shortershorter inin thethe primatesprimates phylogeneticallyphylogenetically moremore distantdistantfromfrom humanhuman..

AR AR –– androgen androgen receptorsreceptors

ppolyolyolyolyolyolyolyoly--------GlGlGlGlGlGlGlGlyy

-- AdditionallyAdditionally , , shortershorter AR AR isoformisoform (87 (87 kDakDa) ) cancan be be producedproduced as a as a resultresult ofof start start ofoftranslationtranslation fromfrom anan internalinternal metioninemetionine, but , but thethe role role ofof thisthis protein, protein, whosewhoseactivityactivity inin vitrovitroisis lowlow, , isis not not characterizedcharacterized..

AR AR –– androgen androgen receptorsreceptors

GynecomastiaGynecomastiainin a a manmanwithwith Reifenstein'sReifenstein'ssyndromesyndrome

-- Point Point mutationmutation inin AR AR maymay resultresult ininacquiringacquiring thethe sensitivitysensitivity ofof AR protein to AR protein to thetheotherother ligandsligands ((includingincluding antianti--androgensandrogens) ) oror to to decreaseddecreasedsensitivitysensitivity to to androgensandrogens. . TheyThey cancanleadlead to to RReifensteineifenstein's's syndromesyndrome

-- SymptomsSymptomsofof insensitivityinsensitivity to to androgensandrogensareare: :

* * gynegyneccomastiomastiaa, , * * atrophyatrophy ofof testestestes, , * * oligospermoligospermoror azoospermazoosperm, , * * increasedincreasedlevellevel ofof gonadotropingonadotropin* * absenceabsenceofof sensesenseofof smellsmell

KennedyKennedy’’ ss SyndromSyndromee

-- NeurogenerativeNeurogenerativediseasedisease((describeddescribedinin 1911 by1911 byDr. Dr. FosterFoster KennedKennedy)y) manifestedmanifestedwithwith ::

* * decreasingdecreasingsensitivitysensitivity to to androgensandrogensinin adultadult men men * * contineouscontineousweaknessweaknessandand atrophyatrophy ofof musclemuscle(e.g. (e.g. facialfacial). ).

-- SymptomsSymptoms resultresult fromfrom lostlost ofof motoricmotoric neuronsneurons.. TheThe most most pronouncedpronounced weaknessweaknessisisobservedobservedinin musclesmusclesofof face face andand tonguetongue. . DiseaseDiseasestartsstarts fromfrom proximalproximal musclemuscle inin thethe thirdthirdto to fifthfifth decadedecadeandand beginsbeginsfromfrom: :

* * weaknessweaknessofof facialfacial andand armarm musclesmuscles,,* * tremortremor ofof handshands, , * * increasedincreasedlevellevel ofof kreatininkreatinin kinasekinase. .

-- PerhapsPerhaps thethe longerlonger polyglutaminepolyglutamine CAG fragment CAG fragment atat NN--terminal AR terminal AR isis associatedassociatedwithwithearlierearlier onsetonsetofof thethe diseasedisease..

-- WomenWomen withwith longlong CAG fragment CAG fragment inin AR do not show AR do not show anyany clinicalclinical symtomssymtoms, but , but theythey havehavesomesomesubtlesubtle neurologicalneurological changeschangeswhichwhich cancan be be detecteddetectedduringduring detaileddetailed examinationexamination. .

TestosteronTestosteronee –– changeschangeswithwith ageage

-- LevelLevel ofof testosteronetestosteronegraduallygradually decreasesdecreaseswithwith ageage, but , but thethe clinicalclinical significancesignificanceofof thisthisdecreasedecreaseisis not not clearclear. .

-- No data No data indicatesindicates thethe correlationcorrelation betweenbetween thethe levellevel ofof testosteronetestosterone andand sexualsexualbehaviorbehavior, , unlessunlessthethe changeschangesareare withinwithin thethe physiologicalphysiological rangerange. .

-- In men In men withwith healthyhealthy gonadsgonads, but , but withwitherectileerectile dysfuctionsdysfuctions, , supplementationsupplementationwithwithtestosteronetestosteronedoesdoes not not givegive anyany benefitsbenefits. . In In hypogonadalhypogonadal men men itit cancan givegive thetheincreaseincreaseinin ejaculationejaculation frequencyfrequency, but , but doesdoesnot not improvesimproves erectionerection itselfitself..

-- AR AR expressionexpressionstartsstarts to to decreasedecreasefromfromthethe ageage2020--3030..

•• NitricNitric oxideoxide isis releasedreleasedfromfrom nervenerve endingsendings oror fromfrom endothelialendothelial cellscells, , andand stimulatesstimulates cGMP cGMP productionproduction. . ThisThis inducesinduces smoothsmooth--musclemusclerelaxationrelaxation by by reducingreducing thethe calciumcalcium ionion concentrationconcentration, , thusthus producingproducing ananerectionerection. . •• TheThe enzymeenzyme PDEPDE--5 5 reversesreverses thisthis cascadecascade ofof eventsevents by by rapidlyrapidlyconvertingconverting cGMP to GMP. cGMP to GMP. AllAll ofof thethe PDEPDE--5 5 inhibitorsinhibitors (e.g. (e.g. sildenafilsildenafil), ), workwork to to inhibitinhibit thisthis enzymeenzyme, , therebythereby continuingcontinuing smoothsmooth--musclemusclerelaxationrelaxation andand prolongingprolonging anan erectionerection..

Carbonmonoxide

testosteron

•• Decline in sexual function with ageDecline in sexual function with age

•• 1290 subjects (401290 subjects (40--7070 yrs)yrs)

•• 9.6% complete ED9.6% complete ED((5.1% at 405.1% at 40yrs to 15% at age 70yrs to 15% at age 70))•• 25.2%25.2% moderate EDmoderate ED•• 17.2%17.2%minimal EDminimal ED

EpidemiologyEpidemiology

52%52%

Erectile DysfunctionErectile Dysfunction (ED)(ED)

�� ED, once thought to be ED, once thought to be psychogenicpsychogenic

�� Later, considered Later, considered androgenicandrogenic

�� Now, found to be predominately Now, found to be predominately vasculogenicvasculogenic

Erectile DysfunctionErectile Dysfunction (ED)(ED)

Prostate gland

-- a sex a sex glandgland inin menmen aboutabout thethe sizesizeofof a a walnutwalnut, , surroundssurrounds thethe neckneck ofofthethe bladderbladder andand urethraurethra . .

-- partlypartly muscularmuscular andand partlypartlyglandularglandular, , withwith ductsducts openingopening intointothethe prostaticprostatic portionportion ofof thethe urethraurethra . .

-- mademadeupup ofof threethree lobeslobes: a center : a center lobelobe withwith one one lobelobe on on eacheachsideside. .

-- secretessecretesa a slightlyslightly alkalinealkaline fluid fluid thatthat formsforms part part ofof thethe seminalseminal fluidfluid ..

SomeSomenuclearnuclear receptorsreceptors(ER, (ER, ARAR, PR) , PR) stimustimu--latelate expressionexpressionofof cyclincyclin D, D, whichwhich activatesactivatesCdk4. Cdk4. ItIt leadsleadsto to phosphorylationphosphorylation ofof pRBpRB, , andandincreasesincreasestranscriptiontranscription ofof genesgenesincreasingincreasingproliferationproliferation ..

OthersOthers receptorsreceptors(VDR, RAR) (VDR, RAR) increaseincreasep21 p21 expressionexpression, , thusthus blockblock CdkCdk activityactivity , , whichwhichkeepskeepscellscellsatat G1 G1 phasephase. .

HumanHumanprostateprostatetissuetissuestainedstainedwithwith androgen androgen receptor receptor antibodyantibody..

ExpressionExpressionofof androgen receptor androgen receptor inin prostateprostate

AndrogensAndrogensareare strongstrongmitogensmitogensfor for prostateprostatecellscells

Stage B

- cancer that can be felt on rectalexamination and is limited to theprostate.

- many Stage B prostate cancersare curable.

Stage A

- cancer that is only found by elevated PSA and biopsy

- not palpable

- localized to the prostate.

- usually curable,

Stage D

-- cancercancerhashasalreadyalreadyspreadspread, , usuallyusuallyto to distantdistantlymphlymph nodesnodes, , bonesbonesoror otherothersitessites..

-- stagestageD D cancercancerisis not not curablecurablebut but isis treatabletreatable

Stage C

- cancer has already spread beyondthe capsule of the prostate intolocal organs or tissues, but has not yet metastasized or jumped to other sites.

- some Stage C cancers arecurable.

SymptomsSymptomswhichwhich maymay inducateinducate for for prostateprostate cancercancer::

* * InabilityInability to to completelycompletelyemptyempty thethe bladderbladder

* * ExtremalyExtremaly slow slow urinationurination

* * RecurrentRecurrent bleedingbleedingfromfrom prostateprostate

* * AnyAny changeschangesdetecteddetectedby by physicianphysicianduringduring per per rectumrectum examinationexamination

* * IncreaseIncreaseinin PSAPSA

ButBut

OftenOften prostateprostate cancerscancersgrowthgrowth slowlyslowly andand many men do many men do wellwell withoutwithout anyany treatmenttreatment

For For olderolder men men withwith otherother seriousseriousmedicalmedical problemsproblems thethe riskrisk involvedinvolved withwith surgerysurgery maymayoutweighoutweigh thethe potentialpotential benefitsbenefits ((thusthus pharmacologicalpharmacological ”” castrationcastration”” isis a a methodmethod ofofchoicechoice). ).

-- InIn AmericanAmerican populationpopulation meanmean numbernumber ofof CAG (CAG (glutamineglutamine) ) repetitionrepetition was was inin suchsuchorder: order: AfrAfr icicananss<<EuropeansEuropeans<<AsiansAsians.. ItIt correlatescorrelateswithwith riskrisk ofof prostateprostate cancercancer..

-- In single In single describeddescribed casecase inin thethe healthyhealthy tissuestissues AR AR hadhad CAG=24, CAG=24, whilewhile inin tumor tumor CAG=18. CAG=18. HoweverHowever, , bothboth lengthslengthswerewere withinwithin thethe normalnormal valuesvalues. .

ProstateProstatecancercancer

-- In In americanamerican populationpopulation AsiansAsiansareare less less riskedrisked for for prostateprostate cancercancer thanthan AfricansAfricans((thethe highesthighest riskrisk ) ) oror EuropeansEuropeans. . ApartApartfromfrom AR AR polymorphismpolymorphism, , thesethese diffediffe--rencesrences cancan alsoalso be be associatedassociated withwithhigherhigher levellevel ofof testosteronetestosteroneinin AfricansAfricansandand//oror lowerlower activityactivity ofof 55αααααααα redureductasectaseininAsiansAsians..

-- In In JapanJapan less less clinicalclinical casescasesofof prostateprostatecancercancer isis noticednoticed thanthan inin USA but USA but ininpostpost--mortemmortem investigationsinvestigations thethe numnum--bersbers ofof prepre--clinicalclinical oror latentlatent tumorstumors ininbothboth countriescountries areare similarsimilar . .

AndrogensAndrogensandand prostateprostate cancercancer

-- AndrogensAndrogens augment augment thethe growthgrowth ofof prostateprostate cancerscancers andand removalremoval ofof androgensandrogens((castrationcastration) ) stronglystrongly decreasesdecreasestumor tumor growthgrowth.. TillTill nownow, , castrationcastration oror pharmacologicalpharmacologicalinhibitioninhibition ofof androgen androgen pathwayspathways remainsremains thethe major major methodmethod ofof prostateprostate cancercancertreatmenttreatment, , despitedespite thethe high high raterate ofof failurefailure , , causedcausedby by hormonehormone--independentindependent growthgrowth ofoftumorstumors..

-- At At earlyearly phasephaseprostateprostate cancercancer respondsrespondsto to decreaseddecreasedlevellevel ofof testosteronetestosterone, but , but laterlater on on itit cancan growgrow withoutwithout hormonehormone. . ItIt cancan resultresult fromfrom::

* * growthgrowth--factorfactor dependent dependent phosphorylationphosphorylation ofof AR AR andand testostosteronetestostosterone--independent AR independent AR activationactivation, , * AR * AR mutationsmutations leadingleading to ligandto ligand--independent independent activationactivation..* AR * AR mutationmutation maymay changechange thethe ligandligand--specificityspecificity, , thusthus AR AR activationactivation maymayoccuroccur inin responseresponseto to nonnon--specificspecific ligandsligands, e.g. , e.g. estrogensestrogens((AlsoAlso antianti--androgensandrogensmaymay usedusedinin therapytherapy cancan stimulatestimulate thethe mutatedmutated AR)AR)..* Tumor * Tumor cellscellsgrowinggrowing independentyindependentyofof AR AR stimulationstimulation areare selectedselected..

HormonalHormonal therapytherapy

1. LHRH 1. LHRH analogsanalogstherapytherapy

* * chronicchronicadministrationadministrationofof luteinizingluteinizinghormonehormone--releasingreleasinghormonehormone(LHRH) (LHRH) analogsanalogsto to blockblock endogenousendogenousproductionproductionofof luteinizingluteinizinghormonehormone..

* * usuallyusuallytakentakenorallyorally by by thethepatientspatientsbut but theytheycancanbe be alsoalsolonglong--actingactingimplantsimplants

* * preventspreventsthethetestestestesandandadrenalsadrenalsfromfrom producingproducingmalemalehormoneshormones

2. Androgen 2. Androgen blockersblockers

* * usuallyusuallytakentakenorallyorally by by thethepatientspatientsbut but theytheycancanbe be alsoalsolonglong--actingactingimplantsimplants

* * inhibitorsinhibitorsofof androgenandrogen--AR AR interactioninteraction

3. 3. InhibitorsInhibitors ofof 55αααααααα--reductasereductase

* * inin combinationcombinationwithwith otherotherdrugsdrugs(e.g. androgen (e.g. androgen blockersblockers))

UsuallyUsuallysuchsuchtreatmenstreatmensimprovesimprovesclinicalclinical outcomeoutcomeevenevenfor for severalseveralyearsyears

TherapiesTherapiesto to preventpreventactivationactivation ofof androgen androgen receptorreceptor

MechanismMechanismby by whichwhichadvancedadvancedprostateprostate tumorstumorsmaintainmaintain androgen receptor androgen receptor signalingsignaling inin a a castratecastrateenvironmentenvironment

EffectsEffects ofof antiandrogenicantiandrogenic hormonalhormonal therapytherapy

AnabolicAnabolic--androgenic steroids (AAS) androgenic steroids (AAS) AAS AAS are syntheticare synthetic derivatives of testosterone originally designed to providederivatives of testosterone originally designed to provide enhanced enhanced anabolic (tissueanabolic (tissue--building) potency with negligiblebuilding) potency with negligibleandrogenic (androgenic (masculinizingmasculinizing) effects. ) effects. •• Approximately,Approximately, 60 different AAS are available that vary 60 different AAS are available that vary in their chemicalin their chemical structure and thus in their metabolic structure and thus in their metabolic fate and physiologicalfate and physiologicaleffects.effects.

•• Three mainThree main classes of AAS have been describedclasses of AAS have been described::

I.I. InjectableInjectable comcompounds derived frompounds derived from esterificationesterification of the 17of the 17ββββββββ--hydroxyl group of testosteronehydroxyl group of testosterone(e.g. (e.g. testosterone propionatetestosterone propionate,, testosteronetestosterone cypionatecypionate)). . EsterificationEsterification retards degradation and retards degradation and prolongsprolongs the duration of actionthe duration of action..

II. III. I njectablenjectable androgenandrogen esters called 19esters called 19--nornor--testosterone derivativestestosterone derivatives(e.g.(e.g. nandrolonenandrolone decanoatedecanoate)). . The substitution at C19 extends theThe substitution at C19 extends thehalfhalf--life.life.

III. III. OrallyOrally activeactive ccompoundsompounds thatthat are are alkylatedalkylated at C17at C17 (e.g. (e.g. 1717αααααααα--methyltestosterone,methyltestosterone,oxymetholoneoxymetholone, , methandrostenolonemethandrostenolone, and , and stanozololstanozolol))..

CClass I and II AASlass I and II AAS may be aromatized and act at themay be aromatized and act at theestrogen receptorestrogen receptor, whereas class III , whereas class III AAS are believed toAAS are believed tohave minimal estrogen receptor actionshave minimal estrogen receptor actions..

*

*

•• AAS were originally developed for the treatment ofAAS were originally developed for the treatment ofhypogonadalhypogonadal dysfunction in men, dysfunction in men, initiation of delayedinitiation of delayed puberty, and growth promotionpuberty, and growth promotion . .

•• They continue to beThey continue to beused today for these treatments, as well as for therapy inused today for these treatments, as well as for therapy in chronic chronic conditions including HIV/AIDS, severeconditions including HIV/AIDS, severeburns, anemia, burns, anemia, etc.etc.

•• HoweHoweverver, AAS administration is now predominantly, AAS administration is now predominantly one of abuse, and the medical one of abuse, and the medical benefits of low doses of AASbenefits of low doses of AASstand in sharp contrast to the potential health risksstand in sharp contrast to the potential health risksassociated with the associated with the excessive doses selfexcessive doses self--administered byadministered by athletesathletes.. ASS ASS areare usedused, , veryvery oftenofteninin concentrationsconcentrations> 40 > 40 timestimes higherhigher thanthan therapeutictherapeutic dosesdoses..

•• AAt that time, more than one million adultt that time, more than one million adult Americans had or were using AAS to increase Americans had or were using AAS to increase physicalphysical strength, endurance, athletic ability or muscle mass. strength, endurance, athletic ability or muscle mass.

•• RRecentecent reports highlight the factreports highlight the fact that the more insidious growth in the abuse of these that the more insidious growth in the abuse of these drugs isdrugs is not among elite athletes, but not among elite athletes, but among adolescent boys andamong adolescent boys andgirlsgirls. .

•• Present estimations Present estimations inin thethe USA USA are are ththe e 4% of high school4% of high schoolstudents have used AAS, and students have used AAS, and the greatestthe greatest increase in AAS use over the past decade has been reportedincrease in AAS use over the past decade has been reported in adolescent in adolescent girls.girls.

•• AAS AAS increaseincreaseaggressivenessaggressivenessbothboth inin men men andand womenwomen. .

•• AAS appear to modulate neural transmissionAAS appear to modulate neural transmissionboth by classical both by classical ARAR--dependent changes dependent changes inin gene transcription and by gene transcription and by nongenomicnongenomic, , allostericallosteric modulationmodulation of specific receptors.of specific receptors.

•• ASS ASS activateactivate AR AR andand possiblypossibly maymay increaseincrease itsits expressionexpression ((somesome maymay possiblypossiblydecreasedecreasethethe expressionexpressionofof PR PR oror ER).ER).

•• ASS ASS changechangethethe expressionexpressionofof GABAGABA AA receptorreceptor andand allostericallyallosterically modulatemodulate itsits activityactivity , , as as wellwell as as thethe expressionexpression ofof enzymesenzymes responsibleresponsible for for thethe synthesissynthesis ofof endogenousendogenousallostericallosteric modulatorsmodulators. .

•• The GABAThe GABAA A receptor provides the major receptor provides the major mechanism for fast actingmechanism for fast acting inhibition in the inhibition in the adult mammalian nervous system. adult mammalian nervous system. ItIt isis tthe he molecular targets of an extraordinarily molecular targets of an extraordinarily diverse range ofdiverse range of toxinstoxins andand drugs thatdrugs thatincludes includes anxiolyticanxiolytic benzodiazepines, sedativebenzodiazepines, sedativebarbiturates, anticonvulsants, barbiturates, anticonvulsants, convulsantsconvulsants(including a number of insecticides), general (including a number of insecticides), general anesthetics,anesthetics,ethanolethanol..

AAS AAS inin menmen

-- ASSASS increasesincreasesthethe levellevel ofof liverliver enzymesenzymesinin thethe bloodblood((e.g.e.g.AST, ALT, AP, LDH)AST, ALT, AP, LDH)

-- ASSASS decreasesdecreases thethe synthesissynthesis ofof endogenousendogenousandrogensandrogens, , leadingleading afterafter longerlonger treatmenttreatment to to hypogonadismhypogonadism ((atrophyatrophy ofof testestestes, , decreaseddecreasedspermatogenesisspermatogenesis)).. TheseThesechangeschangesusuallyusually reversereverseafterafterfinishingfinishing thethe treatmenttreatment. .

-- TheThe secondsecondsymptom symptom isis growthgrowth ofof breastsbreasts ((becausebecausethethe levellevel ofof estrogensestrogensisis increasedincreased) ) andand thesethesechangeschangescancan be be unreversibleunreversible. .

-- Libido Libido isis increasedincreased, but , but inin thethe same same timetime increasedincreasedisis alsoalso frequencyfrequency ofof erectileerectile disordersdisorders..

AAS AAS inin womenwomenASS ASS leadsleadsto:to:

-- disturbuncesdisturbuncesofof ovulationovulation andand menstrualmenstrualcyclecycle..-- malemale--typetype baldnessbaldness, , -- decreaseddecreasedvoicevoice, , -- increasedincreasedlibido, libido, -- developmentdevelopmentofof hairhair patternpattern typicaltypical for for men, men, malemale--patternpattern boldnessboldness-- developmentdevelopmentofof malemale--typetype musculaturemusculature. . -- hypertrophyhypertrophy ofof clitorisclitoris

TreatmentTreatment withwith androgensandrogens inin pregnantpregnantwomenwomen maymay leadlead to to pseudohermapseudoherma--froditismfroditism inin childrenchildren (girls) (girls) andand fetalfetalgrowthgrowth retardadionretardadion. .

WhatWhat wouldwould be be profitableprofitable to to rememberremember inin JuneJune::

-- CausesCausesandand symptomssymptomsofof thyroidthyroid hormonehormone deficiencydeficiency

-- SplicingSplicing formsforms andand modemodeofof actionaction ofof TR.TR.

-- EffectEffect ofof AR AR polymorphismpolymorphism on on riskrisk ofof diseasesdiseases

-- StrategiesStrategiesofof hormonalhormonal therapytherapy inin prostateprostate cancercancer

ThankThank youyou andand seeseeyouyou nextnext weekweek......

SSlideslides cancan be be foundfound inin thethe librarylibrary andand atat thetheHemeHemeOxygenaseOxygenaseFan Fan ClubClub pagepage::

https://https://biotka.mol.uj.edu.pl/~hemeoxygenasebiotka.mol.uj.edu.pl/~hemeoxygenaseARAR--positivepositive