HP Relationships Flashcards
Describe the negative feedback control of somatomedins
- They are produced when GH acts on target tissue.
- They inhibit the secretion of GH by acting directly on the anterior pituitary and by stimulating the secretion of somatostatin from the hypothalamus.
Describe negative feedback control by GHRH and GH
- GHRH inhibits its own secretion from the hypothalamus.
- GH inhibits its own secretion by stimulating the secretion of somatostatin form the hypothalamus.
What are the causes of GH deficiency?
- lack of anterior pituitary growth hormone
- hypothalamic dysfunction
- failure to generate IGF
- growth hormone receptor defifiency
Describe what GH excess results in before and after puberty
Before-> excess GH caused increased linear growth (gigantism).
After-> excess GH caused increased periosteal bone growth, increased organ size, and glucose intolerance.
Describe the hypothalamic control of prolactin release
-prolactin secretion is inhibited by dopamine (prolactin inhibiting factor) secreted by the hypothalamic,
Describe the negative feedback control of prolactin
Prolactin inhibits its own secretion by stimulating the hypothalamic release of dopamine.
What are the actions of prolactin
- milk production
- breast development
- inhibits ovulation by decreasing release of GnRH
- inhibits spermatogenesis by decreasing GnRH
What occurs with prolactin deficiency
Failure to lactate
What occurs with prolactin excess
- Galactorrhea and decreased libido.
- Failure to ovulate.
-caused by hypothalamic destruction. Either from loss of tonic dopamine inhibitory control or from prolactin secreting tumors.
Describe the hypothalamic control of GHRH and somatostatin
- GHRH stimulates synthesis and secretion of GH.
- Somatostatin inhibits secretion of GH by blocking the response of the anterior pituitary to GHRH.
