Endocrine effects of lithium carbonate in healthy premenopausal women:: Relationship with body weight regulation

1. The mechanisms involved in Li-induced weight gain remain unclear. The higher frequency of obesity in women than in men under Li treatment, suggests a role for reproductive hormones. 2. The serum levels of the following hormones were evaluated in healthy young women at diverse stages of a control menstrual cycle, and during Li carbonate (900 mg/day) or placebo administration: prolactin, luteinizing hormone, follicle-stimulating hormone, 17-beta estradiol, progesterone, thyroxine, thyrotropin, cortisol, dehidroepiandrosterone sulfate, free testosterone, leptin and an oral glucose tolerance test, in order to measure the areas under the glucose and insulin curve. The body weight was assessed the day before and the last day of treatment. 3. The Li serum levels 15 hours after the last dose were 0.31 +/- 0.1 mEq/L. No significant changes in body weight and in the normal fluctuations of the reproductive hormones along the menstrual cycle were observed during Li administration. An increase in the serum levels of thyrotropic hormone (p = 0.0001) was the only significant effect of Li, which may predispose to excessive weight gain after prolonged administration of the cation. 4. The remarkable lack of effects of Li on these hormones, question the pertinence of studies conducted in healthy volunteers for the comprehension of the obesity observed in psychiatric patients who may be particularly prone to gain weight under prolonged treatment with high dose of Li.