Thyroidal hormone metabolism in obesity during semi-starvation.

Six obese subjects were studied over a period of 12 weeks whilst on a 1260 kJ (300 kcal) formula diet. Weight loss was initially rapid, but later slowed markedly despite good patient compliance. The basal metabolic rate (BMR) fell in all patients during the study. Plasma triiodothyronine fell in all patients, whilst the plasma half-life of thyroxine increased. Plasma thyroxine, reverse triiodothyronine (reverse T3) and the serum prolactin and thyrotropin response to thyroliberin all showed no significant change.