Endocrinology Flashcards
another name for pituitary
hypophysis
stimulation of anterior pituitary
releasing hormones from hypothalamus travel to pituitary via pituitary (hypophyseal) portal system
anterior pituitary hormones
- corticotroph cells- adrenocorticotrophic hormone (ACTH)
- stimulates production of cortisol (too much = Cushing’s, too little = Addison’s)
- thyroid cells- TSH
- lactotroph cells- prolactin (PRL)
- somatotroph cells- growth hormone (GH)
- gonadotroph cells-
- luteinizing hormone (LH)
- ovulation & testosterone production
- follicle stimulating hormone (FSH)
- regulates functions of ovaries and testes
- luteinizing hormone (LH)
posterior pituitary signaling
direct stimulation by neural impulses from hypothalamus
posterior pituitary hormones
- oxytocin
- releases breast milk and contributes to uterine contractions in labor
- antidiuretic hormone (ADH) aka arginine vasopressin (AVP)
- antidiuretic (water-retaining property)
GH secreting hormone symptoms
(pituitary adenoma)
- cerebral gigantism
- excessive long bone growth if epiphyseal plates not ossified
- prognathism- jaw elongation
- frontal bossing- enlargement of frontal bone convexities
- alveolar ridge enlargement- gaps in teeth
- enlargement of the nose
- enlargement of of soft tissues of hands and feet
- enlargement of heart (cardiomegaly) and organs
- enlargement of soft tissue of upper airway (sleep apnea)
- colonic polyps
- enlargement of sweat glands
growth failure differential
(crossing the growth chart lines)
- severe illness (CF, leukemia, IBD)
- malnutrition/malabsorption
- child abuse/neglect
- hypothyroidism
- GH deficiency
- meds (chemo, seroids)
- genetics
- constitutional growth delay
- achondroplasia- failure of long bone cartilage replication
growth hormone (GH) pathway
- hypothalamus growth hormone releasing hormone (GHRH)
- binds to somatotroph cells of anterior pituitary
- GH released
- GH binds to receptors on hepatocytes of the liver
- hepatocytes produce “insulin-like growth factors” which trigger growth
* somatostatin from hypothalamus inhibits GH release
prolactin pathway
- hypothalamus secretes thyrotropin releasing hormone (TRH)
- binds to anterior pituitary “lactotrophs” to secrete prolactin
* hypthalamic dopamine inhibits prolactin secretion
- glalactorrhea caused by hyperprolactinemia can be a s/e of meds and not a pituitary prolactin-secreting tumor
effects of excess prolactin
- decreased secretion of gonadotropic releasing hormone (GnRH) from hypothalamus -> decreased LH and FSH
- men: no normal sperm development, low testosterone, lacking secondary sex characteristics
- women: FSH- egg maturation not occurring normally, LH- ovaries not secreting adequate estrogen and progesterone -> no puberty or secondary sex traits, amenorrhea
- INCREASED prolactin “turns down” GnRH and causes same symptoms
Tx of prolactinomas
dopamine agonists
(dopamine is prolactin inhibitor)
- cabergoline
hypogonadotropic hypogonadism
problem not with the ovaries/testes but insufficient FSH and LH to stimulate them to secrete their sex hormones
- can be caused by damage to hypothalamus or pituitary
- eating disorders, disease, malnutrition
- Kallmann syndrome- genetic deficiency in GnRH so FSH/LH not secreted
- failure of menses
- neurological
- anosmia- lack of smell
- hyposmia- impaired sense of smell
primary hypogonadism
“failure of the testes or ovaries”
- Turner’s- normal x and dysfunctional/absent x in females
- Klinefelter’s- normal y and 2 x in males
- viral orchitis
- undescended testes
- autoimmune polyglandular syndrome in males and females
* Tx is testosterone or estrogen and progesterone in oral birth control pills
action of ADH
- secreted by posterior pituitary
- binds to cells in collecting ducts of kidneys
- aquaporin 2 gates form causing water to be reabsorbed into bloodstream
normal plasma osmality and regulation
275-290 mOsm/kg
- >295 water is pulled from cells
- <275 water is pulled into cells
regulated by the hypothalamus
- hypothalamic thirst center stimulated
- posterior pituitary signaled to release ADH
causes of osmoregulatory failure
- central / pituitary diabetes insipidus
- nephrogenic diabetes insipidus
causes of central diabetes insipidus
- head/brain injury of hypothalamus or posterior pituitary
- surgery in these areas
- tumors in these areas (macroadenomas)
- genetic degeneration of hypothalamic or pituitary neurons
- idiopathic (50%)
benign tumor in pituitary area seen in children/young adults
craniopharyngioma
symptoms of craniopharyngioma
- diabetes insipidus
- destruction of anterior pituitary (hypothyroidism):
- no TSH
- no ACTH to stimulate adrenal cortex
- no LH/FSH to stimulate gonads
- bitemporal hemianopsia
- tumor impeads on optic chiasm
- loss of peripheral vision- perimetry test warranted
cause of nephrogenic diabetes insipidus
tubular cells in collecting ducts cannot respond to ADH
- genetic defect/absence in ADH receptor, aquaporin channel insertion/action dyfunctional
- lithium meds- impairs signal between ADH receptor and insertion of aquaporin channels
chief complaint in CDI and NDI
polyuria
- urine volume >40 ml/kg/24h (2.5-3L/24h)
polyuria differential and test
- osmotic diuresis
- uncontrolled diabetes: glomerular filtrate hyperosmotic d/t glucose which pulls water out
- CDI
- NDI
- primary polydipsia- excessive drinking
- typically d/t psychiatric disorder
- water deprivation test:
- plasma osmolality increases
- ADH levels increase in NDI and PP, not CDI (can’t)
- DDAVP “desmopressin” given (ADH analog)
- great affect on CDI
- no affect on NDI
- partial affect on PP
NDI and CDI treatments
- CDI: self-administered DDAVP or tumor treatment
- NDI: thiazide diuretics or amiloride
Na+ normal levels and indications
(Na+ largest component in blood this indicates osmolality)
135-145 meq/L
- >145 and <135 indicates a problem EXCEPT 2 false lows
- very high triglycerides
- severe hyperglycemia
- if high Na+ think hyperosmolality
