Serum albumin thyroid hormone binding

Prolonged therapy with methadone causes increases in serum thyroid hormone-binding globulin, triiodothyronine, and thyroxine, as well as albumin, globulin, and prolactin, and these must be monitored (SEDA-15, 71 SEDA-17, 81). 

Lipophilic hormones that use intracellular gene-specific transcription factors include the steroid hormones, thyroid hormone, retinoic acid (active form of vitamin A), and vitamin D (Fig. 11.8). Because these compounds are water-insoluble, they are transported in the blood bound to serum albumin, which has a hydrophobic binding pocket, or to a more specific transport protein, such as steroid hormonebinding globulin (SHBG) and thyroid hormone-binding globulin (TBG). The intracellular receptors for these hormones are structurally similar and are referred to as the steroid hormone/thyroid hormone superfamily of receptors. 

The levels of transthyretin (binds to vitamin A and thyroid hormones in the blood) and serum albumin in the blood may be used as indicators of the degree of protein malnutrition. In the absence of hepatic disease, decreased levels of these proteins in the blood indicate insufficient availability of amino acids to the liver for synthesis of serum proteins. 

A serum protein of molecular weight 61 000, which migrates in front of albumin on serum protein electrophoresis. It has similar functions to albumin but it is particularly important in the binding of thyroid hormones. Low serum levels are found in a variety of conditions including malignancies and liver diseases. 

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