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where are posterior pituitary hormones synthesized?
in hypothalamic nuclei, then transported down axons to be released into circulation
hormones of the anterior pituitary?
what three anterior pituitary hormones share similary structure?
TSH, LS, and FSH all have same alpha sub-unit
GH and prolactin are homologous
Four ways to inhibit Growth hormone.
- 1. somatostatin from hypothal blocks response of ant. pituitary to GHRH
- 2. negative feedback from tissues -- release of somatomedins to affect pituitary and hypothal (stim somatostatin)
- 3. GHRH inhibits itself
- 4. GH inhibits itself by increasing somatostatin
Two ways to inhibit prolactin.
- 1. increasing dopamine (prolactin inhibiting factor), which is what prolactin does for negative feedback
- 2. decreasing thyrotropin releasing hormone (TRH), which is what the hypothal releases
what other hormone does prolactin inhibit, and to what effect?
inhibits GnRH - to inhibit ovulation and spermatogenesis
Hormones of the posterior lobe?
oxytocin and ADH -- homologous
- adh increases aquaporin 2
- oxytocin causes ejection of milk
where does the organification of I2 occur?
- (creation of MIT or DIT)
- -at the junction of follicular cells and lumen
DIT + DIT = ?
t4 + Thyroglobulin, which is shed to lysosome before t4 enters circulation
Three ways to control cortisol release.
- 1. Hypothalamic control (CRH) - neg feedback from cortisol
- 2. Ant. Pituitary control (ACTH) - neg feedback from cortisol
- -ACTH upregulates it's own receptor
- 3. cAMP - secondary messeger for both CRH and ACTH, so a phosphodiesterase inhibitor would stimulate
what controls the release of aldosterone?
- 1. tonic control by ACTH
- 2. renin-angiotensin system (renal perfusion pressure stim)
- 3. potassium (so aldosterone increases K secretion)
where is calcitonin made?
the parafollicular cells of the thyroid
genetic vs gonadal vs phenotypic sex
- genetic is XX XY
- gonadal is testes/ovaries
- phenotypic is internal genital tract and and external genitalia
Two hormones for male differentiation
- 1. testosterone from leydig cells -- growth and differentiation of wolffian ducts, which develop into male internal genital tract
- 2. antimullerian hormone from sertoli cells - causes atrophy of muulerian ducts (which would have become femal internal genital tract)
Explain regulation of the testes.
- 1. Hypothalamic control: GnRH
- 2. Anterior Pituitary: FSH and LH
- -FSH acts on sertoli cells to maintain spermatogenesis. Sertoli cells secrete inhibin for negative feedback
- -LH acts on Leydig cells to promote testosterone synth. Testosterone reinforces effects of FSH on sertoli cells.
- 3. negative feedback control:
- -testosterone inhibits both GnRH and LH release
- -inhibin inhibits FSH release
Puberty initiated by....
- pulsatile GnRH, which promotes pulsatile LH and FSH
- -GnRH up-regulates it's own receptor
Estrogen Synthesis in ovaries.
- 1. LH stimulates Theca cells to produce testosterone
- 2. FSH stimulates granulosa cells to convert testosterone to estradiol
What rescues the corpus luteum from regression if implantion occurs?
- HCG, which is produced by placenta
- -levels peak until weak nine then fade (basically for duration of the first trimester)
What produces estrogen and progesterone during pregnancy?
- First trimester: corpus luteum
- 3rd and 2nd trimester: progesterone produced by placent, estrogens by placenta and fetal adrenal gland (which produces DHEA for the placenta to convert)
Human placental lactogen
HPL: actions similar to GH and prolactin, increases in value throughout pregnancy
Lactation -- during pregnancy
- -estrogens and progesterone stimulate growth and development of breasts
- -prolactin levels increase from estrogen stimulation, but both estrogen and progesterone block it's action
Lactation -- after pregnancy
- -estrogen and prog decrease abruptly, allowing the build up prolactin to act
- -lactation maintained by suckling, which stimulates both oxytocin and prolactin
Effect of Prolactin on ovulation.
- -inhibits GnRH secretion and action of GnRH on ant. pituitary, so FSH and LH levels decrease
- -antagonizes the actions of LH and FSH
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