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23 Cards in this Set
- Front
- Back
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CRH (Corticotropin Releasing Hormone)
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Released from hypothalamus in a pulsatile fashion. Stimulates corticotrophs in the ant. pituitary to secrete ACTH via a GPCR-PKA-cAMP-Ca2+ influx pathway.
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ACTH (Adrenocorticotropic Hormone)
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Released from ant. pituitary in a pulsatile fashion in response to CRH. Acts on adrenal cortex to synthesize and secrete cortisol via a GPCR PKA-cAMP-phosphorylation pathway - rate-limited by conversion of cholesterol to pregnenolone.
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Glucocorticoids
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Synthesized and secreted from the Zona Fasciculata (and a bit in the Reticularis) in response to ACTH. Cortisol targets liver, fat, muscle, bone, skin, CNS, and lymphoid tissue. Main fcn is to raise plasma glucose levels (anti-insulin) via increased hepatic gluconeogenesis. Also immunosuppressive and anti-inflammatory activity. ~90% is transported thru corticosteroid-binding globulin (transcortin). Binds to nuclear receptors in cell cytoplasm and translocate to nucleus.
Inhibit fibroblasts in connective tissue; enhance bone resorption, reduce renal Ca2+ absorption, inhibit TSH; inhibit LH leading to loss of estrogen. |
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Catecholamines
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Fight or flight hormones. Epi/norepi bind to adrenergic receptors (GPCR).
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Mineralocorticoids
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Aldosterone is produced in the zona glomerulosa of the adrenal cortex. Regulates salt balance and EC volume by controlling kidney excretion/reabsorption of sodium. Aldosterone secretion results in Na+ uptake->Na+ retains water retention->increased arterial blood pressure. Also enhances K+ secretion. Loss of aldosterone leads to hypotension and hyperkalemia, excess is opposite.
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Ca2+
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Mostly located in bone, major source is dairy, exists in plasma free or bound to albumin (free is active form so is what is measured).
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Parathyroid hormone (PTH)
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Secreted by the chief cells of the parathyroid gland, acts to increase plasma Ca2+ and is stimulated by hypocalcemia; decreases plasma PO4 by taking it from bone w/ Ca2+ and then decreasing its reabsorption in the kidney. High PO4 levels also stimulate PTH release by promoting deposition of Ca2+ in bone. PTH acts via a GPCR receptor coupled to PKA-cAMP and PLC pathways. Also stimulates 1 alpha-hydroxylase to convert 25-OH Vit D to 1,25-diOH Vit D (active form). Ca2+ and vit D inhibit PTH synth and secr via a GPCR and nuclear receptor, respectively.
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Vitamin D
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Active form is 1,25 dihydroxyvitamin D. Synthesized in skin thru UV exposure. Steroid hormone bound in blood to vit D-binding protein (DBP) and acts to enhance renal calcium and phosphate reabsorption, enhance intestinal calcium and phosphate absorption, stimulates osteoclasts to release Ca2+ from bone. Stimulated by PTH, but inhibits PTH and its own inactive to active 1 alpha-hydroxylation. Levels assessed by measuring 25 OH Vit D.
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Gonadotropin-Releasing Hormone (GnRH)
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pulsatile secretion from arcuate nucleus of hypothalamus; portal blood carries GnRH to the pituitary, where it activates GnRHR (GPCR->PIPC->Ca2+ & PKC) on gonadotrope cells; low-frequency pulses stimulate FSH release, high stimulate LH. GnRH is very low during childhood, but is activated at puberty. Also inhibited by dopamine and stimulated by norepinephrine.
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Luteinizing hormone (LH) in males
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pulsatile secretion stimulated by high frequency GnRH pulses; stimulates testicular Leydig cells to secrete testosterone; stimulates spermatogenesis in conjunction w/ testosterone and DHT. LH-receptor is a GPCR that activates the cAMP system.
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Follicle-Stimulating Hormone (FSH) in males
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pulsatile secretion stimulated by low frequency GnRH pulses; stimulates 1ry spermatocytes to undergo meiosis I to form 2ry spermatocytes; stimulates testicular Sertoli cells to produce androgen binding protein (ABP), which maintains high local levels of testosterone, and Inhibin B (which may help regulate spermatogenesis); acts via a GPCR
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Testosterone
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reduces GnRH pulse amplitude and slows frequency inhibiting LH secretion; secreted from testes starting at puberty, stimulates development of 2ry sex characteristics, triggers growth of testes, matures seminiferous tubules and commences spermatogenesis; exerts effects by binding to the androgen receptor, which is a nuclear receptor in the cytoplasm that translocates to the nucleus upon binding.
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Inhibin B in males
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produced by Sertoli cells located in the seminiferous tubules of the testes upon stimulation by androgens; inhibits FSH secretion at level of ant. pituitary and may help regulate spermatogenesis
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FSH in women
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pulsatile secretion; causes pregranulosa cells to become granulosa cells; stimulates granulosa epithelial differentiation from stratified squamous to cuboidal, mitosis of granulosa cells, and secretion of estradiol by activating aromatase in granulosa cells; lack of FSH suppresses follicle from reaching antral/graafian stage; acts via a GPCR
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LH in women
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pulsatile secretion, causes androgen and progesterone secretiona; rise in estradiol from granulosa cells triggered by FSH causes upregulation of LH receptors on maturing follicle; estrogen rise eventually causes LH surge which triggers ovulation and development of the corpus luteum; also supports theca cells in the ovary that provide androgens; acts via a GPCR.
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Estrogen
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mitogenic hormones that cause endometrial lining of uterus to proliferate and undergo remodeling; estradiol inhibits FSH, but promotes LH secretion at ovulation (LH surge); inhibits dopamine inhibitory response on GnRH; also stimulates LH receptors on theca cells to make more androgens, leading to more estradiol production; causes endocervix to secrete mucus; stimulates vaginal thickening and lubrication; low estrogen enhances FSH/LH synthesis, but not secretion; act mainly via the estrogen receptor, which is a nuclear hormone receptor
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Progesterone
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secreted by luteal cells and is not mitogenic; stimulates thickening of uterine endometrial layer and increased vasculature; LH binds to LH receptors on granulosa and theca cells to facilitate progesterone production; necessary for implantation of embryo; inhibits LH by slowing GnRH pulse frequency; causes endocervix to secrete mucus to impede sperm entry after ovulation; stimulates acinar glands in breast and makes breasts more tender in luteal phase; increases basal body temp; antagonizes estradiol effects thru downregulation of estradiol receptors; in pregnancy, promotes uterine relaxation and inhibits prostaglandins to prevent uterine contractions, and stimulates breast development; acts via a nuclear hormone receptor
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Inhibin A/B
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FSH stimulates the secretion of inhibin from granulosa cells of ovarian follicles; in turn, inhibin suppresses FSH.
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Activin
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in the ovarian follicle, activin increases FSH binding and FSH-induced aromatization, increasing estradiol.
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human Chorionic Gonadotropin (hCG)
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Secreted by trophoblasts to maintain the corpus luteum in order to produce progesterone until the placenta can take over; peaks at ~10 weeks then drops and plateus at ~20; stimulates adrenal and placental steroidogenesis; immunosuppressive.
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motilin
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Decreases in pregnancy; smooth muscle stimulant; combined w/ progesterone effect = constipation, slower stomach emptying, nausea
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prolactin
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Placental prolactin regulates electrolyte flux across the membranes; breast milk production
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human Placental Lactogen (hPL)
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Produced by syncytiotrophoblast; insulin antagonist, but enhances secretion; glucose intolerance to protect availability of glucose for fetus; also promotes lipolysis and proteolysis in the mother
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