Pituitary Dysfunction

Question 1

primary endocrine disorder

Answer 1

-defect is at producing gland

Question 2

secondary endocrine disorder

Answer 2

-producing gland is normal, defect in stimulation

Question 3

tertiary endocrine disorder

Answer 3

-defect of hypothalamic function (two glands removed from target organ)

Question 4

Growth Hormone

Answer 4

• produced from anterior pituitary
• GH = somatotropin, therefore ant pit is somatotropic
• has indirect effects through the liver (produces somatomedins and IGF-1 which makes bones grow - in adolescents, elongates. in adulthood, thickens) and direct effects on fat (promotes lipolysis)
• inhibits glucose utilization by increased insulin resistance

Question 5

biochemistry of GH

Answer 5

• short half-life: unbound in plasma (doesn’t last long in plasma –> gets broken down quickly)
• two hypothalamic hormones control (GHRH, GHIH aka somatostatin), ghrelin recently identified but action unkown

Question 6

Short stature in children

Answer 6

• GH may cause short stature in children (may also be due to renal or liver dz)
• because many factors affect GH levels, broad testing must be done to determine cause of short stature/growth delay
• if they are short, you want to see them stay on their own growth curve, you don’t want to see them jumping from curve to curve
• congenital GH deficiency usually children of normal size at birth expressing delayed growth over first 1-2 years (normal size at birth is b/c mom is influencing them!)

Question 7

Growth hormone deficiency cause

Answer 7

• idiopathic - lack of GHRH from hypothalamus for undefined reason –> this is considered tertiary because it is the hypothalamus that is the issue, but from the perspective of GH, its a secondary issue because it is only one organ removed from the prdeficiency
• Primary causes include pituitary tumors and pituitary agenesis –> causes many other problems because lots of hormones come from the pituitary
• consider panhypopituitarim

Question 8

GH deficiency presentation

Answer 8

• acquired from birth: normal intelligence, short, obese, immature fascies, delayed skeletal growth, delayed sexual maturation, hypoglycemia and seizures in neonate
• acquired later in life: usually tumor related - cardiac risk, central obesity, atherosclerosis, metabolic syndrome; test this deficiency with stimulation studies

Question 9

Growth effects of excess GH

Answer 9

MOST COMMONLY CAUSED BY SOMATOTROPE ADENOMA (can also be caused by tumor of hypothal or other tumors)

• if before closure of epiphyses, gigantism results (from IGF1 stimulation)
• if after closure of epiphyses, acromegaly results (including increased circumferential bone growth)

Question 10

Metabolic effects of excess GH

Answer 10

• increased fatty acid metabolism, increased ketone production, DECREASED glucose uptake, GLUCONEOGENESIS from liver, INCREASED insulin from pancreas (insulin resistance syndrome, ultimately DM)
• HA, visual field defects (bc tumor is pressing on optic chiasm), CN III, IV, VI palsies, secondary deficiency of other pituitary hormones
• excessive sweating, oily skin, weight gain, weakness, fatigue, menstrual changes, decreased libido, HTN, apnea
• increased risk COLONIC POLYPS and COLORECTAL CANCER (more turnover of cells, higher risk of cancer)

Question 11

tx of excess GH

Answer 11

-surgery, reversal of GH/IGF effects

Question 12

Prolactinoma

Answer 12

• prolactin stimulates milk production by female breast during pregnancy - drop of E at birth triggers let down
• PROGESTERONE CAUSES GLAND GROWTH, PROLACTIN CAUSES MILK PRODUCTION
• MCC PITUITARY TUMOR
• F>M
• may be familial, part of MEN-1 syndrome (multiple endocrine neoplasia)
• most are microadenomas which rarely grow (dont need to remove, just manage sxs)
• result of hyperprolactinemia = hypogonadotropic hypogonadism
• May co-secrete GH and cause acromegaly!
• large tumors may cause HA, visual changes, etc.

Question 13

hypogonadotropic hypogonadism in men and women

Answer 13

• women: decreased FSH and LH leads to oligomenorrhea or amenorrhea, glactorrhea (milk production sans baby) common, increased risk osteoporosis
• men: ED, diminished libido, gynecomastia classic but not 100%, never with galactorrhea

Question 14

hyperprolactinemia

Answer 14

• MCC: PREGNANCY
• hypothyroidism
• renal failure
• cirrhosis
• SLE
• Drugs: psychotrpic agents, cimetidine, TCAs, OCP (birth control)
• tx: stop offending agents, dopamine agonists first line, surgery for large or unresponsive tumors, radiation tends to cause global loss of pituitary fn and should be used cautiously