The Arctic Aeromedical Laboratory's Thyroid Function Study A Radiological Risk and Ethical Analysis (1996) / Chapter Skim
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A. Thyroid Function in Health and Disease
A. Thyroid Function in Health and Disease
Pages 75-80
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From page 75... ...
by enzymatic conversion of T4 to T3. T3 is some three to five times more active than T4 in two important effects of thyroid hormones: increase of oxygen consumption and suppression of TSH secretion by the anterior pituitary gland.
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From page 76... ...
Iodide is nearly completely absorbed from the gastrointestinal tract and enters the inorganic pool in the extracellular fluid. The thyroid gland picks up some 75 fig of iodide per day for synthesis of thyroid hormones, and the rest is cleared (excreted)
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From page 77... ...
Such tests are not employed for evaluation of thyroid function today because better methods are now available. URINARY AND SALIVARY EXCRETION STUDIES Since iodide circulating in the body is ultimately disposed of by two competing mechanisms, thyroidal uptake and urinary excretion, urinary excretion bears a reciprocal relationship to thyroidal uptake and is an indirect measure of thyroid function.
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From page 78... ...
have recently described increased serum binding, yet the increased metabolic clearance rate and daily production rate of T3 increased in white men who lived in Antarctica for more than five continuous months; the authors named this change the "polar T3 syndrome" (Reed et al., 19901. UTILIZATION OF li3} AS A DIAGNOSTIC TOOL IN was the first radioiodine to be employed in clinical studies and has a half-life of only 12.6 hours.
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From page 79... ...
Literature review suggests that 400 reds or more of radiation dose is required to cause significant oocyte loss from the gonads (Baker, 19711. This degree of radiation exposure occurs only after therapeutic doses of {~3]
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From page 80... ...
. Some suggest that no radioiodine studies should be done in women who wish to continue breastfeeding (Dydeck and Blue, 19881.
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