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49 Cards in this Set
- Front
- Back
What stimulates prolactin?
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TRH, Dopamine antagonists
sleep, acute stress, sex, chest/nipple stimulation, pregnancy, seizures, antipsychotics |
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What inhibits prolactin
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dopamine
chronic stress, chronic illness, malnutrition |
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What are some causes of increased prolactin?
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Adenoma, pituitary stalk compression, H2 blocker, phenothiazines, TRH
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A prolactin level of >200 indicates what?
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A tumor
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An elevated prolactin but less than 100 ng/ml suggests what?
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A cause other than a tumor
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What stimulates the release of growth hormone? Inhibits?
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Stimulated by GHRH, inhibited by somatostatin. Also stimulated by sleep, acute stress, fasting, hypoglycemia
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How do we evaluate growth hormone production?
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Look at growth hormone levels and IGF-1 levels.
Growth hormones fluctuate, so IGF-1 (somatomedin) is a better test. |
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Underproduction of GH causes?
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Rare cause of dwarfism
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Overproduction of GH?
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Gigantism or acromegaly
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What does LH regulate?
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wants to make hormones! in females: androgens before ovulation and progesterone after ovulation in males: testosterone |
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What does FSH regulate?
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wants to make eggs and sperm! stimulates development of follicles to prepare for ovulation. stimulates proliferation of germ cells to form sperm |
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What stimulates gonadotropins?
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Cyclic GnRH, norepinephrine, light
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What do theca cells produce?
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LH converts cholesterol to androstenedione (hint: tHeca and LH both have H as the second letter in their name)
In fat, this is converted to testosterone in granulosa cell, this is converted to estradiol by FSH |
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How are estradiol and testosterone found in circulation?
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Bound to SHBG or albumin
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How does obesity affect SHBG levels?
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inhibits production
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What part of HCG is tested with the assay
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the beta subunit
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What are the 2 major physiologic causes of amenorrhea?
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Menopause - increased FSH (also increased LH).
pregnancy - increased HCG. |
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What are causes of hirsutism?
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PCOS high LH FSH ratio
Cushing syndrome CAH - high steroid precursors familial - increased 5-alpha reductase |
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How is extracellular calcium forms transported?
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Free 50%, protein bound 40%, complexed 10% (PO4, HCO3)
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How does PTH act?
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Acts on the bone to mobilize calcium from the osteocytes
Also acts on the kidneys to cause loss of the complexing ions increasing free calcium |
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How is calcitriol produced?
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By the kidney, stimulated by PTH
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What does calcitriol do?
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It acts on the bone to increased mobilized CA. Acts on the intestinal tract and increases absorption, and then inhibits PTH production and it's own production.
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What level do you check for VIt D deficiency?
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25-hydroxy vitamin D
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Where is calcitonin produced?
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parafollicular C cells in thyroid, lung
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What is the function of calcitonin?
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Inhibits bone resorption, lowers serum calcium by increasing renal excretion of calcium and phosphate
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How does gadolinium affect calcium?
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Will lead to falsely low calcium results
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What is the halflife of PTH?
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3-5 minutes
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What are the three etiologies responsible for 99% of hypercalcemia cases?
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Hemoconcentration, Primary hyperparathyroidism, Maignancy
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How many hydroxyl groups in 25 OHD? 1,25 dihydroxy vitamin D? 7-dehyrdrocholesterol?
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2, 3 and 1, respectively |
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Causes of hypocalcemia?
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Low albumin, renal failure
Uncommon - hypmagnesemia, malapsorption, vit D deficiency, Hypoparathyroidism, sepsis, shock, pancreatitis |
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What are the labs seen in secondary hyperparathyroidism?
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PTH much higher than primary hyperpara
More severe bone disease Due to chronic hypocalcemia Often associated with high phoshate when due to renal failure |
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What is seen in FHH? (Familial hypocalciuric hypercalcemia)
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Abnormal receptors which dont respond to calcium, leading to more pth and hypercalcemia
Decreased urine excretion of calcium |
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what is macroprolactin? |
high molecular weight form bound either to IgG or prolactin receptor. 10% of people with increased prolactin have macroprolactin |
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in hypopituitism, what order do you see hormones decrease usually? |
GH and gonadotropins early TSH later ACTH last |
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which four hormones have a common alpha subunit and distinct beta subunits? |
TSH, HCG, FSH, LH |
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how can you distinguish central and nephrogenic diabetes insipidus? |
after water deprivation test, give ADH. central DI: urine concentration rises and volume falls nephrogenic DI: no response |
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when is testosterone highest? |
it is highest on rising and declines during the day. morning testosterone declines slowly with older age and obesity |
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what can be used to evaluate the function of the corpus luteum? |
progesterone. must be interpreted based on the day of the cycle |
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what is AMH? what produces it? |
produced by granulosa cells, inhibits excess response to FSH. Declines as follicles are lost. Marker of ovarian reserve. High in PCOS and ovarian hyperstimulation. |
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What are the HCG levels in the following: ectopic pregnancy threatened miscarriage trophoblastic neoplasia |
ectopic pregnancy - slower rate of increase than normal and low for dates. threatened miscarriage - low and falling results. trophoblastic neoplasia - often high for dates, needed to follow treatment. note: ectopic and trophoblastic neoplasia may have abnormal HCG forms not detected by some assays. |
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how can DHEAS (dehydroepiandrosterone sulfate) and testosterone be used to determine source of increased androgens? |
ovarian: increased testosterone but not DHEAS adrenal: increased DHEAS but not testosterone |
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where is PTHrP produced and what does it do? |
produced by most cells but in greatest amounts by fetal parathyroid, squamous epithelial cells and breast epithelial cells. It is involved in bone formation in fetus, calcium mobilization in the mother during pregnancy and lactation and transplacental transport of calcium. |
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which form of vitamin D do you get from plants? sun? |
ergocalciferol - plants. 7-dehydrocholesterol - sun. |
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what test do you do to measure total calcium? what are 2 interferences? |
colorimetric assay. Interferences include chelating agents such as EDTA and gadolinium |
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how do you measure free calcium? |
ion selective electrodes |
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what are 3 etiologies for hypercalcemia? |
hemoconcentration, primary hyperparathyroidism, and malignancy |
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in sarcoid, there can be ectopic production of what? |
calcitroil |
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what are two causes of secondary hyperparathyroidism? |
chronic renal failure and vitamin D deficiency |
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what are four causes of hypoparathyroidism? |
hypoparathyroidism labs: low calcium and high phosphate. causes: surgical removal of parathyroids, autoimmune destruction, DiGeorge syndrome and parathyroid infiltration (hemochromatosis) |