Hypothyroid-like regulation of the pituitary-thyroid axis in stable human immunodeficiency virus infection

Abstract

Thyroid function and regulation were studied in 14 consecutive male outpatients with asymptomatic human immunodeficiency virus (HIV) infection (CDC II/III, n = 8) or AIDS (CDC IV, n = 6) who were free of concomitant infections and hepatic dysfunction, and in eight healthy, age- and weight-matched male controls. Blood was sampled every 10 minutes over 24 hours for measurement of thyrotropin (TSH). Thereafter, thyroid hormones and TSH responsiveness to thyrotropin-releasing hormone (TRH) were measured. Triiodothyronine (T3) and thyroxine (T4) did not differ between HIV-infected patients and controls, but HIV patients had lower thyroid hormone-binding index ([THBI] HIV patients, 1.01 +/- 0.02; controls, 1.11 +/- 0.03; P < .02), free thyroxine (FT4) index (94 +/- 3 v 110 +/- 4, P < .01), FT4 (11.8 +/- 0.4 v 14.3 +/- 0.4 pmol/L, P < .01), and reverse triiodothyronine (rT3) values (0.18 +/- 0.01 v 0.26 +/- 0.02 nmol/L, P < .001) and higher thyroxine-binding globulin ([TBG] 20 +/- 1 v 16 +/- 1 mg/L, P < .02) values. Mean 24-hour TSH levels were increased in HIV patients (2.39 +/- 0.33 v 1.44 +/- 0.16 mU/L, P < .05), associated with increased mean TSH pulse amplitude and TSH responsiveness to TRH. No differences were observed between asymptomatic HIV-seropositive and AIDS patients. In conclusion, there is a hypothyroid-like regulation of the pituitary-thyroid axis in stable HIV infection, which differs distinctly from the euthyroid sick syndrome in non-HIV-nonthyroidal illnesses.(ABSTRACT TRUNCATED AT 250 WORDS)