Hypothalamus and Pituitary Flashcards
Growth hormone def
- most important clinical manifestation of GHD is growth failure
- mediated by IGF-1
- circulating endogenous growth hormone lasts 20-30 minutes
- promotes longitudinal bone growth until epiphyseal closure
Laron dwarfism
-primary GF deficiency
-severe postnatal growth
-GH receptor mutated gene
DX:
-inc circulating levels of GH and low IGF-1 and IGFBP-3
Treatment for Laron syndrome
Mecasermin- recomb IGF-1
Side effect is hypoglycemia- take med w/ meal
Prader- Willi syndrome
Deletion of genes from paternal chr 15
-growth failure, obesity, carb intolerance, mild-mod retardation
Turner Syndrome
girls have 45 x karyotype
-rudimentary ovaries, growth hormone must be used to achieve max height
Other indications for GH
aids, short bowel syndrome (pts dependent on parenteral nutrition)
Toxicities of GH
Hyperglycemia, pseudotumor cerebri, inc risk of sleep apnea in prader willi syndrome
-arthralgias and myalgias, rarely carpal tunnel
contraindicated in individuals with active malignancy
Mecasermin
-recomb IGF-1
Take med with carb containing meal because can cause hypoglycemia
-IGF1 deficiency
-Laron syndrome
Acromegaly
large hands, large feet, frontal bossing, coarse facial features
glucose intolerance
-cardiac manifestations- LV hypertrophy, hypertension,
-GI- colon polyps
-elevated IGF-1
Screening for Acromegaly
elevated IGF-1
Confirmation with post prandial growth hormone- should go down
MRI of brain- most radiologically visible
Tx for acromegaly
transphenoidal surgery
33-75% success rate
- octreotide- somatostatin analogue- normalizes GH in 50% of pts by binding to GH receptor in pituitary adenoma–> tumor shrinkage in 50% of pts
- can cause gall stones
- parenteral administration
2nd line therapy- GH receptor blocking agents peripherally (does not decrease size of tumor)
Pituitary apoplexia
Ischemic necrosis in enlarging adenoma
- comrpession of superior hypophysial artery against sellar diaphragm
- hemorrhage
- rapid enlargement and edema- acute pain, CN palsies, pituitary insuffiency
-if pt has low ACTH and low cortisol- they are in adrenal crisis
Acute adrenal insufficiency
Need to treat right away
-Start steroids
Then treat with mineralocorticoids
Must triple steroid dose in times of acute stress
Levothyroxine
hypothyroidism
taken 1 hr away from food
Testosterone replacement
-do not give to young men who wish to bear children, untreated sleep apnea, prostate or breast cancer
Prolactinoma
Lactoroph adenomas- produce prolactin
-very amenable to pharmacologic therapy
- more common in women
- premenopausal women- , galactorrhea, infertility, oligomenorrhea, amenorrhea
postmenopausal- larger prolactinomas, bitemporal hemianopsia, incidental
men- hypogonadism, dec libido, impotence, infertility, gynecomastia
Cabergoline
Dopamine D2 receptor agonist
Used for shrinking pituiary prolactin secreting tumors, lowers circulating prolacin levels and restoring ovulation
Bromocriptine
Dopamine agonist for prolactinomas
-can cause nausea and vomiting, headache, postural hypotension
Diabetes insipidus
excessive thirst and excreion of large amts of diluted urine because of little ADH production
Tx with desmopressin (long lasting ADH analog for V2 receptor)
Desmopressin
Tx for central diabetes insipidus
Can cause hyponatremia due to excessive reabsorption of water
Nephrogenic diabetes insipidus
Problem with receptor for ADH
-no treatment available
Vasopressin
responsible for regulating body’s retention of water by inc water absorption in collecting ducts (v2 receptor)
-inc peripheral vascular resistance which in turn increases arterial blood pressure (v1 receptor)
Prolactin axis
Hypothalamus- thyrotropin releasing hormone (TRH) which is stimulatory
Dopamine- inhibitory
Pituiary- prolactin
Target organ- mammary gland
Reproductive axis
Hypothalamus- GnRH
Pituitary- LH, FSH
Ovary or testis- estrogen, progesterone, testosterone
Inhibin from ovary and testes have inhibitory
Thyroid axis
Hypothalamus- Thyrotropin releasing hormone (TRH)
Pituitary- TSH
THyroid- T3 and T4
Adrenal axis
Hypothalamus- Corticotropin releasing hormone (CRH)
Pituiary- ACTH
ADrenal- glucocorticoids, mineralocorticoids, sex steroids
