Effect of diazepam (Valium) on dialysable thyroxime.

Introduction Increasing numbers of patients are receiving treatment with the tranquillizing drugs, and patients referred to hospital with suspected thyrotoxicosis are often taking such drugs. It is important to know what effects these drugs have on tests of thyroid function if diagnostic confusion is to be avoided. Diazepam is a commonly prescribed centrallyacting tranquillizer. Published work on its effect on thyroid function is both scanty and conflicting. It has been said to inhibit thyroxine formation (Todays Drugs, 1969, Brit. med. J.). Both diazepam (Valium) and chlordiazepoxide (Librium) have been shown to depress the uptake of iodine by the thyroid gland in thyrotoxicosis and thus obscure the diagnosis of hyperthyroidism (Harvey, 1967; Turner & Sneddon, 1967). Clarke & Hall (1970), using radioactive iodine uptake and clearance, protein-bound iodine and tri-iodothyronine resin uptake, have investigated fourteen euthyroid and six mildly thyrotoxic patients and could detect no significant difference in the results of these tests before and during treatment with chlordiazepoxide over a 4-week period. Mazzaferri & Skillman (1969) found significant day-to-day fluctuations in radio-active iodine uptake and protein-bound iodine tests in twentyfour healthy adults on diazepam. However, they were unable to confirm that thyroid function was altered by diazepam. The conflicting reports concerning the effects of diazepam on thyroid function may be due to an