Thyroxine binding and cellular metabolism of thyroxine in mononuclear blood cells from patients with anorexia nervosa

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Abstract
Nuclear binding of thyroxine (T4), cellular deiodination of T4 and nuclear accumulation of endogenous triiodothyronine (T3) were investigated in mononuclear blood cells from 8 patients with anorexia nervosa. Although the patients were euthyroid, serum T3 was depressed and serum reverse T3 increased. The nuclear maximal specific binding capacity (msbc) for T4 in cells from patients with anorexia nervosa was increased (2.4 .times. 10-16 mol T4/10 .mu.g DNA, P < 0.01) as compared to that of normal subjects (msbc = 1.1 .times. 10-16 mol T4/10 .mu.g DNA), whereas the Ka did not differ from that of normal subjects (Ka = 2.2 .times. 109 vs. 3.0 .times. 109 l/mol). Cellular deiodination of T4 was significantly depressed (Vmax = 4.0 .times. 10-17 mol iodine/106 cells per min) as compared to that of normal subjects (Vmax = 2.0 .times. 10-16 mol iodine/106 cells per min), whereas nuclear accumulation of endogenous T3 was normal (Vmax = 3.09 .times. 10-19 mol T3/10 .mu.g DNA per min). Three patients started to gain weight and, concomitantly with the normalization of serum T3, the nuclear T4 capacity returned to normal. Cellular deiodination of T4 did not normalize within the observation period. Patients with anorexia nervosa, in which serum T3 is depressed, have an increased capacity of nuclear T4 receptors. The cellular 5''-deiodinase is inhibited but nuclear accumulation of endogenous T3 is normal.