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We studied the serum concentrations of total testosterone (T), unbound T, dihydrotestosterone (DHT), total estradiol-17β (E2), unbound E2, and luteinizing hormone (LH) in 15 hyperthyroid men with Graves' disease, 4 of whom had gynecomastia. The mean serum T concentration of 1895 ng per 100 ml in hyperthyroid patients was significantly higher than the mean value of 621 in normal men. It could be explained by an increase in serum concentration of sex hormone binding globulin (SHBG) in hyperthyroidism; the mean serum unbound T, 21.9 ng per 100 ml, in hyperthyroid patients was not statistically different from the corresponding value of 17.3 in normal men. Serum DHT concentration was also elevated in hyperthyroid patients. Similarly, the mean serum E2,. 10.8 ng per 100 ml, in hyperthyroid men, was significantly greater than the corresponding mean value of 2.7 in normal men. However, it could not be explained entirely by elevation of serum SHBG in hyperthyroidism. The average unbound E2, concentration, 135 pg per 100 ml, in patients under study, was also higher than the corresponding value of 55.6 in normal men; it was comparable to the mean value of 144 in normal women. The ratio of serum total E2 to T(E2/T*100) averaged 0.57 in hyperthyroid men, which did not differ significantly from the mean ratio of 0.43 in normal men. The mean ratio of unbound E2, and unbound T of 0.65 in hyperthyroid men was, however, significantly higher than that of 0.34 in normal men. The mean serum LH concentration was also elevated in hyperthyroid patients. The values of serum T. DHT and unbound T in presence of gynecomastia were not different from those in its absence. However, serum EL>, unbound E2,, unbound E2/T and LH were significantly higher in patients with gynecomastia than in those without it. It is proposed that (i) alterations in balance between circulating unbound estrogen and unbound androgen may have a significant role in genesis of gynecomastia in hyperthyroidism, and (ii) the combination of the findings of supranormal serum LH, elevated total E2, unbound E2, total T and a normal serum unbound T in hyperthyroid men may be a result of supranormal setting of hypothalamo-hypophyseal-gonadal axis, presumably due to enhanced production or effectiveness of hypothalamic luteinizing hormone releasing hormone (LHRH) in hyperthyroidism. Normal serum unbound T under these circumstances would suggest some limitation in testicular secretion of T in response to LH in patients with hyperthyroidism.
CHOPRA et al. (Fri,) studied this question.