Lymphocyte thyroid hormone receptors in obesity.

Triiodothyronine (T3)-receptor characteristics of isolated circulating human mononuclear cells have been studied in a group of obese patients who claimed to be unable to lose weight on conventional 4.2 MJ (1000 kcal) diets. The cells of the obese patients exhibited a lower receptor capacity than those of a control group of non-obese subjects but the difference was not significant. There was a significant fall (P less than 0.01) in receptor capacity in the obese patients after 12 weeks in a 1.34 MJ (320 kcal) per d formula diet and this provides a further mechanism whereby a fall in metabolic rate takes place in response to severe dietary restriction. Some patients who also received T3 (60 micrograms/d) in addition to the formula diet showed a further fall in the receptor numbers. These findings may partly account for the previously reported resistance to thyroid hormones in obesity.