A prospective controlled study of the impact of hyperthyroidism on reproductive function in males

The aim of this prospective controlled study was to ascertain the effect of hyperthyroidism on sperm quality and composition. We studied 23 thyrotoxic male patients, aged 43.8 +/- 2.4 yr (mean +/- SEM), and 15 healthy male controls of approximately the same age (42.2 +/- 2.2 yr). Two semen analyses at intervals of 2-3 wk were obtained before and about 5 months after euthyroidism was achieved either by methimazole alone (14 patients) or (131)I plus methimazole (9 patients). Total fructose, zinc (Zn), and magnesium (Mg) were also measured in seminal plasma in 16 patients, because 7 had semen volume less than 2 ml. In the control group semen analysis was performed only once. Mean (+/-SEM) semen volume was within normal range both in patients (3.3 +/- 0.2 ml) and controls (3.5 +/- 0.4 ml; P = NS). Mean sperm density was lower in patients, although the difference compared with controls did not reach statistical significance (35.7 +/- 5.3 vs. 51.5 +/- 6.1 x 10(6)/ml; P = 0.062). The same was found with sperm morphology (68 +/- 7% vs. 78 +/- 8%; P = NS). Finally, mean motility was lower in thyrotoxic males than in controls (28 +/- 8% vs. 57 +/- 7%; P < 0.01). After treatment, sperm density and motility improved [35.7 +/- 5.3 vs. 43.3 +/- 6.5 x 10(6)/ml (P = NS) and 28 +/- 8% vs. 45 +/- 7% (P < 0.05), respectively], but sperm morphology did not change (68 +/- 7% vs. 70 +/- 6%; P = NS). Mean values for fructose, Zn, and Mg did not differ between controls and patients either before or after achievement of euthyroidism [9.2 +/- 0.7, 3.0 +/- 0.5, and 4.2 +/- 0.7 nmol/liter vs. 8.6 +/- 0.9, 3.0 +/- 0.5, and 4.7 +/- 0.8 nmol/liter (patients before) and 9.1 +/- 0.7, 3.1 +/- 0.6, and 4.5 +/- 0.9 nmol/liter (patients after treatment) for fructose, Zn, and Mg, respectively]. Moreover, according to the treatment given, no statistically significant differences were found before or after treatment. Finally, seminal plasma fructose, Zn, and Mg levels did not correlate with sperm parameters or with pretreatment thyroid hormone levels. In conclusion, the results of our study indicate that male patients with hyperthyroidism have abnormalities in seminal parameters, mainly sperm motility. These abnormalities improve or normalize when the patients become euthyroid. Restoration of sperm parameters was independent of the treatment provided for the hyperthyroid syndrome. Moreover, seminal plasma elements, such as fructose, Zn, and Mg, did not correlate with sperm density, motility, or morphology.