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Neuroendocrine
- Adenoyhypophysis: fenestrated capillarieso Pars distalis
Chromatophils Acidophils
o Somatotrophs (40-50%) Growth hormone; inhibited by IGF-1
fromliver and high glucose levels; hypoplasia
somatotrophslow GHdwarfism in
children; hyperplasiagigantism;
hyperplasiapituitary adenoma
acromegaly (adults)
o Mammotrophs (15-20%) Prolactin: secretion inhibited by
dopamine (dominant negative
regulation); stimulus is suckling
Basophils:o Thryrotrophs (5%)
Thyroid stimulating hormone
activatesthyrotrophsTSHthyroidT3/T4
productionT3 negative feedback loop
Hypothyroidism (low thyroid activity =low T3/T4))
Pituitary defect: produces lowTSH, therefore low T3/T4
Thyroid defect: high TSH, butT3/T4 still low because of
thyroid
Hyperthyroidism (high thyroid activity) Pituitary defect:
produces high
TSH, therefore high T3/T4
Thyroid defect: low TSH, but highT3/T4 because of thyroid
o Gonadotrophs (10%) FSH
Females: promote development offollicles in the ovaries,
promote
granulosa cells to proliferate in
order to form mature follicleo Follicle produces estradiol,
activin, and inhibin
(inhibitor of gonadotroph
Males: act on the Sertoli cells in theseminiferous tubules
o Sertoli cells responsible formaking androgen-binding
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protein, responsible for
concentrating testosterone
LH Females: acts on corpus luteum,
transiently formed in the second
half of the menstrual cycleo Corpus luteum makes
progesterone; considered a
transient endocrine gland
o LH levels remain highduring pregnancy
Males: acts on the Leydig cells inthe seminiferous tubules
o Responsible for makingtestosterone
*Low levels of FSH and LH will result in
infertility in both sexeso Corticotrophs (20%)
Corticotrophin-releasing hormonecorticotrophsACTHadrenal
glands
(zona fasciculate of the cortex) cortisol
ACTH stimulates growth andfight/flight response toget moving
Aldosterone responsible forresorbing water through
collecting
tubules of the kidneys
o Metabolized in liver, buthigh levels causehypertension b/c
of
increased blood volume
o High levels cortisolnegative feedback shut off
corticotrophs and pituitary
glands
High levels of stress stimulate ACTH Adenomamany
corticotrophs
patient always ready to go, nervousness,
hypertension
Cushings diseasehypoplasia ofcorticotrophslow ACTH/cortisol
unable to control weight, low energy;
looks like chronic condition but its not
(prescribed ACTH)
Chromatophobes
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o Pars tuberalis Wraps up the infundibular process and forms the
pituitary
stalk
Most cells are gonadotrophs secreting low levels of FSH/LHnot
physiologically significant
o Pars intermedia Leftover from Rathkes pouch inner layer
- Neurohypophysiso Pars nervosa: composed of capillaries,
sinusoids, unmyelinated axons
and pituicytes
Unmyelinated b/c speed doesnt matter but they need thepituicytes
to perform
Lipofuscin deposit increases with ageo Infundibulum
Infundibular process Unmyelinated axons, which make up the
hypothalamoneurohypophyseal tract, originating from
2 nuclei within the hypothalamusthe hormones
produced in the hypothalamus migrate down the axons
and are stored in the pars nervosa until released by the
portal system
o Paraventricular nucleus: oxytocin Oxytocin acts on uterus to
promote
contraction of myometrium during
labor/induce labor; also involved in
lactation and stimulates myoepithelium
around the glands to contract to forcemilk out of the ducts
Also a mood regulator and works byrepresing the amygdala:
treatment of
PTSD, autism and mood disorders
o Suproptic nucleus: vasopressin (ADH) Acts on the kidney
collecting tubules to
reabsorb water and increase blood
pressure
Low vasopressin neurogenic diabetesinsipidus (hypothalamic
diabetes
insipidus, HDI); differ from nephrogenicdiabetes insipidus (NDI)
by ADH levels
HDI: low production of ADH NDI: mutation in ADH receptor
Median eminence- Pineal Gland
