Pituitary and Thyroid Flashcards
Which hormones are peptide hormones? Steroid hormones? Amino acid derivatives?
- insulin, glucagon, ACTH, PTH, prolactin
- cortisol, aldosterone, estrogen, testosterone, progesterone
- epi and norepi, thyroid hormones
What is the hypothalamus made of?
paraventricular and supraoptic nuclei, with axons that make up stalk that connects to PPG/
What type of tissue is the APG/? PPG/?
APG/ - glandular tissue
What connects the APG/ to the H/?
hypothalamo-hypophyseal-portal system
What hormones are made by the hypothalamus?
Dopamine (prolactin inhibiting factor), CRH, GHRH, TRH, GnRH, GHIH (somatostatin), ADH, Oxytocin
What hormones are made by the APG/?
GH, ACTH, TSH, FSH, LH, Prolactin
What hormones are secreted by PPG/?
ADH and oxytocin
What type of cells secrete GH? What will this do?
Somatotrophs, stimulate secretion of insulin-like growth factor from liver + effect on long bones etc..
What is somatostatin? What synthesizes it? What does it do?
GH-inhibiting hormone, secreted by hypothalamus and GI tract to decrease GH
How is dopamine secreted? By what?
Continuously secreted to inhibit prolactin by H/
What triggers H/ to stop secreting dopamine?
Suckling of infant
Where are hormones stored in the posterior pituitary?
Herring Bodies (dilations in axons)
When is ADH secreted? What is it’s MOA?
when high blood osmolarity or low blood volume/BP, retains H2O from urine + vasoconstriction of blood vessels
What is the action of oxytocin?
dilates cervix + stimulates uterine contractions during childbirth + makes breast muscle cells contract during breastfeeding + increases during orgasm and pleasant social interactions
Where is the pineal gland? What is it made up of? What does it secrete?
behind H/ and pituitary, made up of pinealocytes which secrete melatonin
What does melatonin do? What secretes it?
regulates circadian rhythm (sleep/wake cycle), secretion by pinealocytes
What cells secrete Calcitonin? What gland is this?
Parafollicular cells (c-cells) of the thyroid
When is aldosterone secreted? By what? MOA?
with low BP or high serum K+ = prevents H2O and Na+ loss, increases K+ elimination, secreted by zona glomerulosa of adrenal gland
What does zona fasciculata secrete? What does this do?
Cortisol, stress hormone secreted during fight or flight + stimulate osteoclasts + increases blood sugar
What does the zona reticulata secrete?
sex hormone precursors/androgens
What is the blood supply to and from the adrenal glands?
afferent = branches of suprarenal arteries Efferent = large medullary veins go to suprarenal veins
What cells secrete PTH?
Chief/principal cells of parathyroid
Where does the pituitary gland sit?
Anteroinferiorly to H/, inferior to optic chiasm, in sella turcica of sphenoid bone of skull
What type of cells of the pituitary gland are chromophils? What does this mean? Which of these are acidophils vs basophils?
Chromophils = cells that produce hormone, are stainable
Acidophils (stain pink): somatotroph (GH), mammotroph (Prolactin)
Basophils (stain blue/purple): gonadotrophs (FSH/LH), corticotroph (ACTH and alpha-MSH), thyrotroph (TSH)
What do corticotrophs secrete?
ACTH and alpha-MSH
What is alpha-MSH? What does it do? Where is it secreted from?
alpha-melanocyte stimulating hormone, leads to secretion of pigment from melanocytes, secreted from corticotrophs
What hormones act on prolactin?
Dopamine (inhibits), TRH (stimulates)
What is another name for ADH?
vasopressin
What cells are found in the PPG?
pituicytes - modified glial cells that help insulate nerve fibers, increase speed of impulse conduction
From what does the PPG arise from?
evagination of diencephalon (neuroectoderm) of the 3rd vesicle
From what does the APG arise from?
outpouching of roof of oral ectoderm/mouth (Rathke pouch) - glandular. Apoptosis at base of pouch
Which pituitary lobe is more vascularized?
Anterior since hormones have to diffuse
What blood vessel feed infundibulum? What about the different pituitary lobes?
Internal carotid artery branches into inferior and superior hypophyseal arteries. Superior supplies infundibulum and anterior lobe, inferior supplies posterior
Where are the capillary plexuses formed in the pituitary? What are they made of?
- Superior hypophyseal artery forms primary capillary plexus around infundibulum, and secondary plexus in anterior lobe
- Inferior hypophyseal artery forms its own capillary plexus in posterior lobe
What causes hyperpituitarism?
Pituitary adenoma (tumor, >99% benign)
How are pituitary adenomas diagnosed?
Headache/visual field deficits –> elevated hormone levels + MRI of pituitary
What is considered a microadenoma? Macroadenoma?
micro <1cm
macro>1cm
What are the sxs associated w/ pit. adenomas? (general)
Visual changes (tumor presses on optic nerve, optic chiasm right above it), acute headaches, hormone changes
What type of visual deficits can be seen w/ pituitary adenomas?
Bitemporal hemianopia (temporal vision loss in both eyes), monocular visual field deficits (loss of vision in specific quadrant), junctional field deficits (partial loss of vision or blind spot)
What are the sxs associated w/ pituitary adenoma that originates within gonadotrophs?
Usually no sxs
What are the sxs associated w/ pituitary adenoma that originates within thyrotrophs?
hyperthyroidism = heat intolerance, weight loss, anxiety, diarrhea, moist skin, heart palpitations
What are the sxs associated w/ pituitary adenoma that originates within somatotrophs in adults? What are complications associated?
Acromegaly = coarsening of facial features, enlarged hands, thickening of skin, and prognathism (jaw protrusion) secondary to pharyngeal soft tissue growth –> obstructive sleep apnea, cardiomyopathy, HTN, osteoarthritis, increased risk of cancers
What are the sxs associated w/ pituitary adenoma that originates within somatotrophs in children?
Gigantism
What are the sxs associated w/ pituitary adenoma that originates within corticotrophs?
Cushing disease (2ndary hypercortisolism) = hyperpigmentation, purple skin striae, HTN, weight gain, moon-shaped face, truncal obesity, skin changes, hyperglycemia
What are the sxs associated w/ pituitary adenoma that originates within lactotrophs?
irregular/ absent menses, infertility, galactorrhea (milky discharge), decreased libido, hypogonadism
Macroadenomas = visual field deficits
What is the tx for pituitary adenomas that show neurological sxs?
surgery (transsphenoidal sinus approach)
What is the tx for pituitary microadenomas?
no surgery unless GH or ACTH hypersecretion
What is the tx for pituitary adenomas when surgery contraindicated?
treat elevated hormone, ex: high GH = give octreotide or lanreotide, high prolactin = treat w/ cabergoline or bromocriptine
If surgery contraindicated and no reponse to meds, what is a possible x for pituitary adenomas?
radiation
What is panhypopituitarism?
Multiple hormones are synthesized less (should see decrease in ACTH)
What are possible causes of hypopituitarism?
tumors (pituitary adenoma, tumor compresses pituitary blood supply), head trauma, pituitary surgery, stroke, granulomatous disease, Sheehan syndrome (infarction of PG/ after postpartum hemorrhage), Empty Sella Syndrome (enlarged sella turcica)
What is Sheehan syndrome? What does it cause? Sxs?
infarction of pit. gland after postpartum hemorrhage, causes hypopituitarism –> hypotension, post-delivery lethargy, anorexia, weight loss, inability to breastfeed
What is Empty Sella Syndrome? What does it cause? Sxs? What is seen on imaging?
enlarged sella turcical due to high CSF pressure causing herniation of subarachnoid space into sella, pit. gland flattened on MRI, asymptomatic
What are symptoms associated with decreased prolactin production?
can’t lactate after delivery, decreased reproductive function
What are symptoms associated with decreased GH production in children? In adults?
Children = short stature Adult = increased fat mass, decreased bone mineral density, dyslipidemia, increased atherosclerosis
What are symptoms associated with decreased ACTH production?
2ndary cortisol deficiency -
Mild cases: postural hypotension and tachycardia
Severe cases: weight loss, fatigue, decreased libido, hypoglycemia
Worst cases: hypotension, shock, death due to vascular collapse (cortisol needed for peripheral vascular tone maintenance)
What are symptoms associated with decreased FSH/LH production?
Hypogonadotropic hypogonadism: sterility, decreased libido
Women only - decreased estradiol secretion = hot flashes, sxs of vaginal atrophy (dryness, bleeding)
Men only - low testosterone causing infertility, decreased energy, low libido
What are symptoms associated with decreased TSH production?
2ndary hypothyroidism - fatigue, cold intolerance, decreases appetite, constipation, facial puffiness, dry skin, bradycardia, depression, anemia
What are symptoms associated with decreased ADH production?
Central diabetes insipidus since K excretes high-volume dilute urine = leads to dehydration, increased thirst, and dizziness