Radioiodine thyroid hormone replacement

So far no definite therapeutic applications have been described for TRH. It has been suggested that it has antidepressant effects, but further controlled studies (M15) did not substantiate the initial reports. The role of TRH as a tool in the treatment of thyroid carcinoma (by increasing uptake of the therapeutic dose of radioiodine by the tumor) (F4) is as yet not confirmed. TRH could be used in the treatment of hypothalamic (tertiary) hypothyroidism, but it does not offer any advantage over thyroid hormone replacement. We have not observed any beneficial effect of TRH in regenerating thyroid remnants after surgery. It has been reported that TRH administration to cows results in an elevation of PRL which increases milk production (K3). Further controlled studies of the applications of TRH in the dairy industry are required. 

In 50 women taking levothyroxine either for primary thyroid failure or for hypothyroidism secondary to radioiodine treatment for hyperthyroidism, there was no difference between the two groups in terms of bone density at the hip or spine and no difference from the reference population (31). In addition, there was no correlation between bone density and circulating thyroid hormone concentrations or duration of levothyroxine replacement. These findings are reassuring, although large studies of fracture risk are required, in view of previous evidence of an adverse effect of levothyroxine on bone mineral density, especially in post-menopausal women (32). 

Liothyronine Tabs. Liothyronine is the most rapidly effective thyroid hormone, a single dose giving maximum effect within 24 h and passing off over 24—48 h. It is not used in routine treatment of hypothyroidism because its rapid onset of effect can induce heart failure. Its main uses are in myxoedema coma and psychosis, both rare conditions. A specialised use is during the withdrawal of levothyroxine replacement (to permit diagnostic radioiodine scanning) in patients with thyroid carcinoma. 

Fig. 3 Biochemical monitoring of a patient during treatment for thyroid disease. This 55-year-old woman was first diagnosed as hyperthyroid, and received radioiodine therapy. She became profoundly hypothyroid, and was treated with thyroxine. Her thyroid hormone results at first indicated good replacement, but recently they indicate that she Is under replaced. It is possible that she Is not taking her thyroxine tablets regularly.

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