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Flashcards in week 9- endo 2 Deck (80)
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• TSH testing:

o measures pit stim of thyroid
o ↑: thyroid doesn’t make enough T4 (1st hypo)
o ↓: 1) hyperthyroid, 2) abn pit doesn’t make TSH (2nd hypo)


• Thyroid hormone state:

o free=available for uptake
o bound=circulating storage pool


• T4 tests:

o Total T4: bound + free. ~99% on TBG (doesn’t enter tissues)
o fT4/fTI (index): Free; measured direct or calc as fTI= free/bound. helps tell if abn T4 is dt abn TBG (pg, viral hepatitis, cirrhosis, breast CA)


• Triiodothyronine (T3)

o ↑: hyperthyroid (st ↓TSH, ↑T3 & T4 mb normal)
o Hypothyroid: T3 mb normal (w ↑TSH, ↓T4)
o PG and OCPs: ↑ both total T4 & T3


• N TSH, N fT4, NT3:

o Euthyroid


• N TSH, N/↑ fT4, N/↑T3:

o Euthyroid hyperthyroxinemia


• N TSH, N/↓ fT4, N/↓ T3:

o Euthyroid hypothyroxinemia


• ↑ TSH, N fT4, N T3:

o Subclinical hypothyroid


• ↑TSH, ↓fT4, N/↓T3:

o Primary hypothyroid


• ↓TSH, N fT4, N T3:

o Sunbclinical hyperthyroid


• ↓TSH, ↑/N fT4, ↑T3:

o Hyperthyroid


• T3-Resin uptake:

o serum inc w radiolabeled T3 tracer
o insoluble resin added to trap remaining unbound radio-T3
o Result: % tracer bound to resin (inverse of # free binding sites for T3)
o Distinguish TBG excess and def from hyper/hypo-thyroid


• ↑ tT4, ↑T3RU, ↑FTI:

o Hyperthyroid


• ↑ tT4, ↓T3RU, N FTI:

o TBG excess


• ↓ tT4, ↓T3RU, ↓ FTI:

o Hypothyroid


• ↓ tT4, ↑T3RU, N FTI:

o TBG def


• Serum Reverse T3:

o rT3 = biologically inactive, dt deiodination of T4 (diff enzyme), mainly in liver
o ↓ T3 & ↑ rT3: mb ssx hypothyroid → ↑ protein synthesis and O2 consumption by all cells
o ↑ rT3: mb chronic dz, Wilson’s syndrome


• Anti-thyroid antibodies (ATA):

o a-TG: (+) in Hashimoto’s
o a-thyroperoxidase (a-TPO): catalyzes iodination of tyrosine; ↑ in Hashimoto’s
o TSH receptor (TRAb)


• TRH test:

o serum TSH measured after inj w TRH to determine if thyroid problems dt ↓ TRH (3rd hypothyroid, rare)


• Thyroglobin (Tg):

o Monitor w thyroid CA w thyroid glands removed
o =protein produced by normal thyroid cells and thyroid CA cells


• Radioactive Iodine Uptake (RAIU):

o swallow sm amt radioactive iodine
o ↑: thyroid gland is overactive
o ↓: underactive


• Thyroid Scan:

o may show diffusely high or low intake or discrete (nodular) areas of high (Hot nodule) or low (cold nodule) intake
o gets a “picture” of the gland


• Ultrasound:

o used to determine if a nodule is solid or cystic


• Goiters

o = enlarged thyroid gland; diffuse or nodular
o Mb seen in normal, hypo/hyperthyroid
o Geographical differences in incidence dt I def
o Etio: I def (endemic goiter), ↑TSH, Grave’s, Pg
o Many of no clinical significance but full assessment needed
o Ssx: often asx. Early: pressure/lump in throat, choking sensation, dyspnea, dysphagia


• Goiter staging:

o Normal: ~20g in size
o 0: not visible; non-palpable
o 1: possibly visible; mb palpable, ↓40 g
o 2: visible; easily palpable, ~40 g
o 3: visible, palpable, > 40g


• Goiter work-up:

o Labs: TFTs, ATAs
o neck x-rays, thyroid scan, US w needle bx = gold standard for dx


• Euthyroid (Simple) Goiter:

o dt ↓thyroid fxn w/o clinical dz.
o Etio: Endemic, pg, menopause, hormone effects, I
o goitrogens interfere w I uptake (Brassicas, soy, peanuts, millet, strawberries, peaches, sweet potato, etc)
o drugs (amino-salicylic acid, sulfonylureas, lithium)
o Labs: ↑TSH, ↓T4 in hypothyroid


• Thyroid nodules:

o Usu benign, scan to r/o malig
o Labs: TSH, FT4, ATA titers, serum Ca
o Thyroid US, fine-needle aspiration bx
o Thyroid scan: “hot” nodules in hyperfxn, “cold” in non-fxn, “warm” = nodule w normal fxn


• Hypothyroidism, causes:

o F > M, tends to be familial; gland mb small and fibrotic, or goiter
o Causes: inherited enzymatic defects, AI, RAI exposure, anti-thyroid drugs, dietary goitrogens, thyroidectomy, inflam, granuloma, neoplasms, congenital aplasia, pituitary failure


• Hypothyroid ssx:

o weak, fatigue, lethargy, cold intolerance, wt gain
o anorexia, constipation, hair loss, dry hair, dry coarse cold skin
o dyspnea, myalgias/arthralgia, paresthesias
o irregular menses, infertility, periorbital edema, thick tongue, ascites
o pallor, ↓reflexes, anemia, bradycardia, effusions, vitiligo, goiter
o CTS, eyelid dropp, psychosis, ↓facial expression, carotenemia
o ↑heart, hoarseness, poor memory, hypothermia, myxedema coma