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where are posterior pituitary hormones synthesized?
in hypothalamic nuclei, then transported down axons to be released into circulation
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hormones of the anterior pituitary?
- -GH
- -TSH
- -prolactin
- -LH
- -FSH
- -ACTH
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what three anterior pituitary hormones share similary structure?
TSH, LS, and FSH all have same alpha sub-unit
GH and prolactin are homologous
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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
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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
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what other hormone does prolactin inhibit, and to what effect?
inhibits GnRH - to inhibit ovulation and spermatogenesis
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Hormones of the posterior lobe?
oxytocin and ADH -- homologous
- adh increases aquaporin 2
- oxytocin causes ejection of milk
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where does the organification of I2 occur?
- (creation of MIT or DIT)
- -at the junction of follicular cells and lumen
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DIT + DIT = ?
t4 + Thyroglobulin, which is shed to lysosome before t4 enters circulation
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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
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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)
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where is calcitonin made?
the parafollicular cells of the thyroid
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genetic vs gonadal vs phenotypic sex
- genetic is XX XY
- gonadal is testes/ovaries
- phenotypic is internal genital tract and and external genitalia
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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)
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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
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Puberty initiated by....
- pulsatile GnRH, which promotes pulsatile LH and FSH
- -GnRH up-regulates it's own receptor
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Estrogen Synthesis in ovaries.
- 1. LH stimulates Theca cells to produce testosterone
- 2. FSH stimulates granulosa cells to convert testosterone to estradiol
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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)
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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)
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Human placental lactogen
HPL: actions similar to GH and prolactin, increases in value throughout pregnancy
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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
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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
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Effect of Prolactin on ovulation.
- prolactin:
- -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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