Pituitary Flashcards
Anterior lobe of pituitary
Rathke’s pouch
Ectodermal diverticulum
Hormones: “FLAT PiG”
FSH LH ACTH TSH Prolactin Intermidate – MSH GH
Posterior lobe of pituitary
Invagination of hypothalamus – neuroectoderm
ADH
Oxytocin
ADH
Decrease urine output
Vascular constriction
Increase ADH: nicotine, opiates
Decrease ADH: ethanol, atrial natriuretic factor, decrase serum osmolality
Oxytocin
Uterine contraction – induced by cervix dilation
Milk ejection – stimulated by suckling
Inhibited by alcohol and stress
GnRH
Pulsatile release leads to FSH and LH secretion
Inhibited by prolactin
Continuous GnRH – inhibits FSH and LH
FSH
Granulosa cell follicle development
Spermatogenesis
Inhibited by inhibin
LH
Progesterone production
Theca lutein cells
-ovulation
-form corpus luteum
Leydig cells -> testosterone
Inhibited by progesterone and testosterone
ACTH
Release stimulated by CRH and stress
Inhibited by cortisol
Acts on adrenal cortex to release cortisol
MSH
Intermediate lobe of pituitary
-> melanin release by melanocytes
TRH
Stimulates TSH release, acts on thyroid to release T3, T4
Inhibited by T3, T4
GH
Stimulated by GHRH, exercise, sleep, puberty, hypoglycemia, estrogen, stress, endogenous opioids
Cause: Release of IGF-1 -> growth Decreased glucose uptake Increased protein synthesis Increased organ size Increase lean body mass
Inhibited by GHIH (somatostatin), somatomedins, IGF1, obesity, pregnancy, hyperglycemia
Prolactin
Stimulated by TRH
Causes milk production and secretion, breast development
Inhibits ovulation
Inhibits GnRH
Release inhibited by dopamine
POMC
Precursor to ACTH and MSH
Contains hormonal peptides sequence for: lipotropin, beta-endorphin
Primary adrenal insufficiency
Production of cortisol low
Hypothalamus and pituitary make ACTH, trying to stimulate the adrenals to make more cortisol
When ACTH concentration is excessive, MSH receptors in skin are stimulated -> skin hyperpigmentation
Hyperprolactinemia
MC anterior pituitary hormone abnormality
Causes by:
Pregnancy/nipple stimulation
Stress – physical or psychological
Prolactinoma – assoc w/ bitemporal hemianopia
Dopamine antagonists – anti psychotics (haloperidol, risperidone), domperidone, metoclopramide
Premenopausal female sx: hypogonadism -> infertility, oligo/amenorrhea, rarely galactorrhea
Post menopausal: no sx – already hypogonadal
Males: hypogonadism (low T) -> decreased libido, impotence, infertility (low sperm counts), gynecomastia, rarely galactorrhea
Pituitary adenoma
Prolactinoma -> Amenorrhea Galactorrhea Low libido Infertility Bitemporal hemianopia
Tx: bromocriptine, cabergoline (DA agonists)
Surgical resection
Acromegaly
Too much GH
Adult
Large tongue – deep furrows, indentations (teeth)
Increased spacing of teeth Deep voice Large hands and feet Coarse facial features Impaired glucose tolerance -> DM
Dx: elevated IGF-1
OGTT – check GH level not glucose
-normally glucose suppresses GH
Tx: surgical resection
Octreotide
Gigantism
Too much GH in kids
Excess bone growth of linear bones
Tall and big children
Dx: elevated IGF-1
OGTT – check GH level not glucose
-normally glucose suppresses GH
Tx: surgical resection
octreotide
Somatostatin
D cells in GI mucosa
Pancreatic islet cells
Nervous system
Actions:
Reduces splanchnic blood flow, reduces GI motility, gallbladder contraction, inhibits secretion of most GI hormones
Deceases exocrine secretions in the pancreas
Decreases hormone secretion in CNS, PNS, endocrine organs
Clinical uses of somatostatin analogs
octreotide, somatostatin LAR, lanreotide –P
pituitary excesses (except prolactin): acromegaly, thyrotropinoma, ACTH-secreting tumors
GI endocrine excess: Zollinger-Ellison Sn, carcinoid sn, VIPoma, glucagonoma, insulinoma
Diarrheal diseases
Need to reduce splanchnic circulation: portal hypertension (bleeding varices), bleeding peptic ulcers
Sheehan syndrome
Postpartum hemorrhage -> underperfusion of pituitary
Pituitary necrosis and hypopituitarism
Aglactorrhea d/t deficiency of prolactin
Amenorrhea after delivery
Secondary hypothyroidism -> fatigue, cold intolerance, wt gain
Hyponatremia (rare)
