Phosphodiesterase Activity in Human Subcutaneous Adipose Tissue in Hyper- and Hypothyroidism

Abstract

Phosphodiesterase (PDE) activity was determined in sc adipose tissue from 12 patients with untreated hyperthyroidism, 8 patients with untreated hypothyroidism, and 10 healthy nonobese subjects. Eight of the hyperthyroid group were reexamined after treatment when they were euthyroid. The apparent V_maX of the low K_m form of PDE was 25% lower in untreated hyperthyroidism (P < 0.05) and 100% higher in untreated hypothyroidism (P < 0.01) than in the controls; treatment of the hyperthyroidism resulted in normalization of the value. There was a positive correlation between the mean fat cell volume and the V_max of the low K_m PDE in all conditions (r = 0.64-0.85). As regards the high K_m form of PDE, the V_max values for both hyper- and hypothyroid patients did not differ from those for the control group. The results of this study suggest that in man, the apparent V_max for the PDE with low K_m is determined by the thyroid hormones.