Denatured TBG does not bind iodothyronines but can be detected with antibodies that recognize the primary structure of the molecule (23). In euthyroid adults with normal TBG concentration, about one-third of the molecules carry thyroid hormone, mainly T4. When fully saturated, it carries about 20 µg of T4/dl of serum. The biologic half-life is about 5 days, and the volume of distribution is similar to that of albumin (34,35) (Table 1). TBG is cleared by the liver. Loss of sialic acid accelerates its removal through interaction with the asialo-glycoprotein receptors reducing the half live by 500-fold (21). However, it is unknown whether desialylation is a required in the normal pathway of TBG metabolism.
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Synthroid is taken orally regardless of the reason for use. For the purpose of treating hypothyroidism Synthroid doses will most commonly fall in the 100-150mcg per day range. They may be slightly higher for large individuals, but this will be determined after a period of use has passed. For the purpose of performance based fat loss, use will normally start around 50mcg per day and gradually increase as needed. With short-term use (approximately 6 weeks) the dose is increased 25mcg per day every 1-3 days until the maximum dose is reached. Doses rarely surpass 150-200mcg per day. For long-term use (approximately 12-16wks) the dose is increased -25mcg every 2-3 weeks as needed with the same 150-200mcg per day dose not being surpassed.