Pituitary physiology III Flashcards
When is prolactin secreted (time of day, life events)
incr. during preg and lactation
episodic secretion. begins after sleep and peaks 4-7 am. not a circadian rhythm, but a sleep-dependent one
What factors inhibit prolactin seccretion
dopamine
acts via D2 receptors in anterior pituitary.
describe regulation of prolactin secretion
TRH and VIP promote prolactin secretion from the anterior pituiary, as does sleep and hypothyroidism
decrease in estrogen and progesterone after delivery
What classes of drugs induce sustained hyperprolatcinemia
antipsychotics (haloperidol, risperidone, etc), antidepressants (tricyclics, MAO-I), buspirone, alprazolam, prokinetics (metoclopramide), antihypertensives (alpha-methyldopa, reserpine, verapamil), morphine, H2 antagonists (cimetindine, ranitidine)
What are some results of hyperprolactinemia
hypogonadism
women: shortened luteal phase, anovulation, oligomenorrhea, infertility
males: decr. testosterone synthesis and spermtogenesis
What is macroprolactin
high molecular weight complexes of prolactin and immunoglobulin
benign clinical condition
Where is TRH synthesized
supraoptic/supraventricular nuclei of the hypothalamus
When is TRH stimulated?
vasopressin and alpha adrenergic agonists stimulate TRH synthesis
also found in pancrease, GI, prostate, and testes
Kallman syndrome
no smell; GnRH deficiency prevents onset of puberty
What should I know about feedback regulation of thyroid function?
T4 and T3 have negative effects
dopamine decreases TSH
glucocorticoid excess impairs sensitivity of pituitary to TRH– lowers TSH
estradiol incr. sensitivity to TRH- incr. serum TSH
What factors inhibit LH and FSH secretion
Testosterone, estrogen, progesterone
inhibin in in men
What hormones are important in PCOS
somewhat controversial, but we think that it is related to elevated LH levels. LH stimulation may cause excess ovarian androgen levels
Commonalities btw ADH and oxytocin
posterior pituitary hormones
both made as prehormones
borth released in response to an action potential
Diabetes insipidus
abosolute or relative deficiency of ADH leading to polyuria
may be primary if due to excess fluid intake
or may be central if there is abnormal decrease in the synthesis and secretion of ADH
may be nephrogenic if the kidneys stop responding to ADH
What does oxytocin do?
stimulates myoepthelial contractions in the uterus during parturition and in the mammary gland during lactation
