THE EFFECTS OF THYROID STATUS ON PLASMA LEPTIN LEVELS IN WOMEN

Leptin, the product of the adipose specific ob gene, regulates food in take and energy expenditure. However, little is known about the effect s of thyroid status on plasma leptin levels in women. We determined fa sting plasma leptin levels before and 1 month after restoration of eut hyroidism in 20 female patients with hypothyroidism, 20 female patient s with hyperthyroidism and 20 age and BMI - matched female controls. T o restore the normal thyroid function patients with hypothyroidism wer e treated with levothyroxine, whereas patients with hyperthyroidism we re treated with propylthiouracil. Plasma leptin levels were measured b y a RIA method with a sensitivity of 0.5 mu g/l. Leptin levels were si gnificantly lower in patients with hypothyroidism before treatment (4. 17+/-2.58 mu g/l) than in patients with hyperthyroidism (6.80+/-4.3 mu g/l; z=-2.06, p=0.037). Leptin levels were significantly higher in hy perthyroid patients than in the control group (3.71+/-1.69 mu g/l, z=- 2.44, p=0.014) whereas leptin levels in the hypothyroid patients were not significantly different from those in control subjects (z=-0.16, p =0.87). Restoration of euthyroid state was not associated with a signi ficant change in leptin levels either in the hypothyroid (from 4.17+/- 2.58 to 5.22+/-3.4 mu g/l; z=-1.74, p=0.08) or in the hyperthyroid gro up (from 6.80+/-4.37 mu g/l to 7.93+/-6.25 mu g/l z=-0.89, p=0.37), al though a tendency for leptin to increase was observed in both groups. There was no correlation between plasma leptin and FT3, FT4, TSH, or B MI either before or after therapy in both groups. Leptin levels were s ignificantly correlated with BMI in the control group (r=-0.53, p=0.01 8). We conclude that plasma leptin levels are increased in hyperthyroi dism and unchanged in hypothyroidism. Furthermore, our study demonstra tes that mean plasma leptin levels are not influenced by short term re storation of euthyroidism in both hypothyroidism and hyperthyroidism, although an effect of long-term treatment may not be excluded. (J. End ocrinol. Invest. 21: 337-341, 1998) (C)1998, Editrice Kurtis.