Week 1 - Endocrine Flashcards
Group 1 Hormones
steroids, thyroid
lipophilic, transported bound to proteins
long plasma half life
intracellular receptors (thyroid=nuclear, steroid=cytoplasmic) - act on transcription/translation
Group 2 Hormones
Peptides, proteins, glycoproteins, catecholamines
hydrophilic, transported freely
short half-life
plasma-bound receptors
mediators: cAMP, cGMP, Ca, metabolites, kinases
Origin of pituitary components
hypophyseal diverticulum (Rathke's pouch) anterior wall= pars distalis superior extension= pars tuberalis posterior wall= pars intermedia Infundibulum= stalk + pars nervosa
Origin of thyroid components
thyroid diverticulum (endoderm)= thyroid follicular cells Neural crest= parafollicular cells Dorsal wing of pharyngeal arch 3,4 (endoderm)= parathyroid principal cells
Primary germ layer origin of glands
pituitary= ectoderm thyroid/parathyroid= endoderm adrenal= mesoderm
Hyperprolactinemia
Causes:
-prolactinoma (most common)
-drugs (metoclopramide, risperidone, D2 antagonists)
-infundibular stalk compression (from larger pituitary mass)
-pregnancy, lactation, stress, sleep
Sx: women have menstrual abn, galactorrhea, men have ED and hypogonad
Tx: dopamine agonists (cabergoline, bromocriptine), very effective
Acromegaly
excess growth hormone (GH)
GH stimulated by GHRH, inhibited by somatostatin and IGF-1(feedback from liver)
Sx: skull and extremity growth, thick skin, etc
Dx: serum IGF-1, or oral glucose tolerance test
Tx: surgery, radiation, octreotide, lanreotide, pegvisomant
Things pituitary releases
Anterior: ACTH- glucocorticoids (stim by CRH) TSH- T3,T4 (stim by TRH) GH- IGF-1 (stim by GHRH, inhi by somatostatin,IGF-1) Prolactin- (inhib by dopamine) Gonadotropins- FSH and LH (stim by GnRH) Posterior: vasopressin(ADH), oxytocin
Growth hormone deficiency
Sx: in neonate= hypoglycemia,, in child= fat, microphallus, delayed puberty, short
Tx: rGH, check IGF-1 to dose
PTH feedback loop
low Ca - PTH secretion -
- kidney: Ca reabsorption, convert 25 to 1,25 vitD
- Intestine: Ca absorption
- Bone: Ca resorption (and P)
Calcium sensing receptor (CaSR)
expressed in parathyroid and kidney
loss of fxn= familial hypocalciuric hypercalcemia (FHH)
gain of fxn= autosomal dominant hypocalcemia (ADH)
Primary hyperparathyroidism
hypercalcemia (PTH dep)
usually sporadic, single tumor
MEN (multiple endocrine neoplasias)
Familial isolated hyperparathyroidism
Familial hypocalciuric hypercalcemia (FHH)
ectopic PTH (rare)
Sx: hyperparaosteitis, brown tumor (bone), thinning of bone cortex
Familial hypocalciuric hypercalcemia (FHH)
CaSR loss of fxn (usually, not always) autosomal dom asymptomatic, lifelong PTH not suppressed use 24hr urine Ca and creatinine to rule out
PTH independent hypercalcemia
PTH is low malignancy calcitriol-mediated (granulomatous, sarcoid) -excess vitD hyperthyroidism (inc bone resorbtion) immobilization milk --PTHrP
Tx of hypercalcemia
fluids, loop diuretics (furosemide)
bisphosphonates (inhibit osteoclasts)
Hypocalcemia lab findings ddx
primary hypoparathyroid: PO4 up/n, PTH down/n, vitD n
Pseudohyperparathyroid (PTH resistant): PO4 up/n, PTH up, vitD n
Mg depletion: PO4 n, PTH down/n, vitD n
secondary hyperparathyroid: PO4 down/n, PTH up, vitD down
Hypoparathyroidism
hypocalcemia, PO4 up
either genetic or autoimmune or infiltrative
Sx:basal ganglia calcification, hypocalcemic tetany (hand contraction)
Pseudohyperparathyroidism
PTH resistance
GNAS mutation
Albright’s Hereditary Osteodystrophy= short, round face, short 4th metacarpals, ossifications
Hypocalcemia flow chart
PTH down or nl= probable hypoparathyroidism, r/o Mg def
PTH up with high phos= PTH resistance, renal insuff
PTH up with low/n phos= vitD def, occult malabsorption ,, measure 25vitD and 24hr urine Ca and creatinine, check for celiac ds, check BMD