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23 Cards in this Set

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CRH (Corticotropin Releasing Hormone)
Released from hypothalamus in a pulsatile fashion. Stimulates corticotrophs in the ant. pituitary to secrete ACTH via a GPCR-PKA-cAMP-Ca2+ influx pathway.
ACTH (Adrenocorticotropic Hormone)
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.
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.
Fight or flight hormones. Epi/norepi bind to adrenergic receptors (GPCR).
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.
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).
Parathyroid hormone (PTH)
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.
Vitamin D
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.
Gonadotropin-Releasing Hormone (GnRH)
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.
Luteinizing hormone (LH) in males
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.
Follicle-Stimulating Hormone (FSH) in males
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
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.
Inhibin B in males
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
FSH in women
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
LH in women
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.
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
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
Inhibin A/B
FSH stimulates the secretion of inhibin from granulosa cells of ovarian follicles; in turn, inhibin suppresses FSH.
in the ovarian follicle, activin increases FSH binding and FSH-induced aromatization, increasing estradiol.
human Chorionic Gonadotropin (hCG)
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.
Decreases in pregnancy; smooth muscle stimulant; combined w/ progesterone effect = constipation, slower stomach emptying, nausea
Placental prolactin regulates electrolyte flux across the membranes; breast milk production
human Placental Lactogen (hPL)
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