DanaObeidat

SamahFreihat

Diseasesoftheendocrinesystem2020lecture1:Pituitarygland

DrFatimaObeidat

Endocrinesystemdiseases

generalprinciples1- Masseffectmeansanenlargementoftheglandwhichcancompressadjacentstructures. E.g: pituitary gland diseases, like benign pituitary tumors (adenomas) , might compress adjacent normal tissue decreasing the secretion of its hormonal causing hypopituitarism.• Masseffectcanbeduetoneoplasticornon-neoplasticconditions• Neoplasticinclude:adenoma(Benign) andcarcinoma(Malignant)• Nonneoplastic=hyperplasia (non-neoplastic lesion characterized by the

No. of the cells in a particular organ)

The endocrine system is made of highly integrated and widely distributed organs called endocrine glands. The goal of theses glands is to reach a metabolic state of equilibrium and they do so by secreting hormones.

Endocrinesystemdiseasesgeneralprinciples

2- Endorganresistancemeansthattheglandissecretingthehormonebutthetargetorganisnotrespondingtoit.Thisoccursinsometypesofdiabetes.End organ resistance means that the gland/organ is secreting a normal amount of hormone, but the target organ is not responding to it. E.g: , the endocrine cells of the pancreas secretes insulin but the target tissues (adipose cells and skeletal muscle cells) are unresponsive to the action of insulin leading to hyperglycemia & type 2 diabetes.

PITUITARYGLAND:THEORCHISTRAMAESTRO

• Because Thehormonessecretedfromthepituitaryglandcontrollevelsofhormonessecretedfromallotherendocrineglands.E.g: Adrenal gland

Pituitary gland• Small,beanshapedstructurethatliesatthebaseofthebrainwithinthesella turcica.

PituitaryglandThis Figure shows the pituitary gland siting in Sella Turcica. In the right part of the figure, you can see the hypothalamus which lies above the pituitary gland, and it controls the secretions of the pituitary gland by its post. & Ant. Lobes. E.g. CRH secreted from the hypothalamus that controls the secretion of ACTH from the pituitary gland. Also, the hypothalamus secrete hormone like ADH & Oxytocin that are stored in the posterior pituitary gland.

يكرتلا جرسلا =Sellaturcica =pituitaryfossa

• Thesella turcica (LatinforTurkishseat)isasaddle-shapeddepressioninthebodyofthesphenoidboneoftheskull.

Thehypothalamus( pituitarythecontrols( داھملا تحت( ةیماخنلا ةدغلا )

Theproductionofmostpituitaryhormonesis controlledbypositivelyandnegativelyactingfactorsfromthehypothalamuswhicharecarriedtotheanteriorpituitarybyaportalvascularsystem.An example on positively acting factors: CRH (corticotropin releasing hormone) which controls the secretion of ACTH (adrenocorticotropic hormone) from the anterior lobe.An Example on negatively acting factors: Dopamine that inhibit the secretion of prolactin from the anterior lobe.

• Thepituitaryglandiscomposedoftwomorphologicallyandfunctionallydistinctcomponents:theanteriorlobe(adenohypophysis) -adeno-because it's composed of epithelial cells andtheposteriorlobe(neurohypophysis)

• Theanteriorpituitaryconstitutesabout80%ofthegland.And secrete six hormones such as TSH, FSH, ACTH, LH, Growth hormone and prolactin.

• The post. Lobe is called the neurohypophysis because it's derived from the neural crest, and it stores some hormones that are stored in the hypothalamus like ADH & Oxytocin.

AnteriorVSPosteriorpituitaryPosteriorLobeofthe

PituitaryGlandAnteriorLobeofthe

PituitaryGland

It's composed of modified glial cells (like those in the brain) and axons extending from the hypothalamus to the posterior lobe.

It's composed of 3 types of epithelial cells:Acidophilic cells >> pink cytoplasm.Basophilic cells >> blue cytoplasm.Chromophobe cells >> cytoplasm’s color is between blue and pink.

Hint:Youcanrefertothenestslide forbetterunderstanding.

ANTERIORVERSUSPOSTERIORPITUTARYLOBESANTERIOR PITUITARY POSTERIORPITUITARY

histology Epithelial cells(Derived from the developed oral mucosa)

Glialcellsandneuronalaxons

Embryological origin Oralmucosa Neuralcrest

Hormonessecreted TSH,PRL,ACTH,GH,FSH,LH.

ADH andoxytocin(synthesized inhypothalamusbutstoredinposteriorpituitary)

Anteriorpituitaryadenohypophysis

• Theanteriorpituitaryiscomposedofepithelialcellsthatsecretetrophichormoneslike:TSH,PRL,ACTH..

Anteriorpituitary/epithelialcells

Explained before

Posteriorpituitary§ Theposteriorpituitaryconsistsofmodifiedglialcells(pituicytes)andaxonalprocessesextendingfromthehypothalamusthroughthepituitarystalktotheposteriorlobe(axonterminals).

§ Theposteriorpituitarysecretes oxytocinandantidiuretichormone(ADH,alsocalledvasopressin).

§ These(OxytocinandADH)aresynthesizedinthehypothalamusandstoredwithintheaxonterminalsintheposteriorpituitary

Diseasesoftheanteriorpituitarygland

1. Masseffect- Massesthatcanaffectthepituitary:adenomas(more common) orcarcinomas

- Adenomascanbe• secretory (secreteoneofthepituitaryhormones)inthiscasethelevelofthathormonewillincrease=hyperpituitarism

• ORadenomascanbenonsecretorysolevelofpituitaryhormonesunaffected=normalhormonallevels

- HOWEVER,ifanon-secretoryadenomaenlargestotheextentitcompresses thesurroundingnormalpituitarytissuethenlevelofhormonesecretionfromthenormaltissuewillbedecreasedresultinginhypopituitarism.

NOTE:pituitarycarcinomasarerareand usuallynon-secretory.

Masseffectsofpituitaryadenomasorcarcinomas

Signsandsymptoms:1.Radiographicabnormalitiesofsellaturcica:Ø sellar expansion,if the tumor is too large.Ø bonyerosions,of sphenoid bone especially in malignant

tumors.2.Compressionoftheopticchiasm(theX-shapedstructureformedatthepointbelowthebrainwherethetwoopticnervescrossovereachother) resultinginvisualfieldabnormalities.3.elevatedintracranialpressure: headache,nausea,vomiting. (Ifthepituitarytumorislarge)

Note:-anymassinthecranium(insidetheskull)cancauseincreasedintracranialpressure4.seizures.5.Cranialnervepalsies.(abnormalities in the functions of cranial nerves)6.pituitaryapoplexy(to be discussed later)

TheopticchiasmistheXshapedstructureformedbycross-overoftheopticnerves.ThepituitaryisveryclosetothischiasmSo:amassinthepituitarycancompressthechiasm..Thiswillaffectvision.

Note:becauseofthiscrossover,therightopticnervesuppliesthelefteyeandviceversa..Soadefectintherightopticnervewillcausevisualfielddefectinthelefteye(thecontralateraleye)

Thisfigureshowtherelationbetweenthepituitaryglandtheopticchiasm.TheOpticChiasmissuperiortheGland.

Optic Chiasm

Pituitaryapoplexy= ةیماخنلا ةتكسلا

• Acutehemorrhageintoanadenoma,whichcausesrapidenlargementofthelesion.Thiswillresultindecreasedconsciousness.

• Thisisaneurosurgicalemergency….Cancausesuddendeath. - or loss of consciousness -

• Thewordapoplexymeansangerorrage.

Pituitaryadenomas• Functional(secretory) ornonfunctional(non-secretory).1- Functional:usuallyonecelltypeandonehormone (Only)produced.• Classifiedaccordingtothehormonestheyproduce. E.g:

prolactin secreting adenoma, ACTH secreting adenoma, etc..

Typesofpituitaryadenomas

• Prolactinomas(prolactin secreting adenoma) >>20-30%>>Themostcommon

• Nullcelladenoma>>20%>>Nonsecretory(But can compress nearby normal tissue causing hypopituitarism)

• ACTH celladenoma>>10-15%• TSHcelladenoma>> 1%>> Leastcommon• Pleuri-hormonal>> 15%(Secrete multiple hormones and

its clinical manifestation corelate to the hormones that it secretes.)

notes1.TSHadenomasarerare >>Soifyouhaveapatientwithhyperthyroidism(which is an increase in the function of Thyroid Gland) ,itwillbeveryrarethatthecauseofhisdiseaseisrelatedtothepituitary.Usually, the cause is related to the Thyroid Gland.2.pleuri-hormonaladenomasdoexist -and they account for 15% of all pituitary adenomas- >> Soapituitaryadenoma,althoughusuallyproducesonehormone,itmightsecretemorethanonetypeofhormonesandpatientswillhavesymptomsrelatedtothehormonessecreted.

Pituitaryadenomas

• Inclinicalpractice10%ofintracranialneoplasms arepituitaryadenomas.

• Butpituitaryadenomascanbeanincidentalfindingin25%ofautopsies.• Peak:4th to6th decades.• Mostlysinglelesions=solitary. - Single lesion >> Multiple

lesions -• Canbedividedintomicroandmacroadenomasaccordingtosize..Cutoffpoint:1cm. (( If the size of the adenoma is less that 1cm it's a micro adenoma, but if its size is more than 1cm it's considered a macro adenoma))

Macroscopicappearance

Grossfeaturesofadenomas- Theusualadenomaisawell-circumscribed,lesionthat ifsmall,isconfined bythesellaturcica.

- In 30%ofcases,theadenomasarenon-encapsulatedandinfiltrateadjacent bone,duraandbrain.

Pituitaryadenoma

This is a macro-Pituitary adenoma in which the size of the lesion is larger than 1cm and it is a non-encapsulated tumor.