Hypothyroidism Has an Adverse Effect on Human Spermatogenesis: A Prospective, Controlled Study

Abstract

Hypothyroidism has an adverse effect on human spermatogenesis. Morphology is the only sperm parameter that is significantly affected. Motility may also be affected, but further studies regarding this are needed. Screening for thyroid dysfunction in males who present with a defect in spermatogenesis is strongly recommended, and if hypothyroidism is noted, the response to thyroid hormone should be evaluated before initiating other treatments.

Inhibin B Levels in Hypothyroid Males

“…Thyroid hormone receptors have been reported in the testis (17); T 3 stimulates Sertoli cell function and mRNA expression of inhibin B and regulates Leydig cell function as well. In humans, hypothyroidism has effects on spermatogenesis with morphological changes and alteration in sperm motility (18). In rats, hypothyroidism results in arrested proliferation of germ cells (19) and in hypothyroid rams in reduced sperm motility (18).…”

“…However, in hypothyroid males, testosterone and free testosterone are low and estradiol levels are normal (18,24) and have no apparent impact on gonadotrophin secretion because there is no reciprocal increase in FSH and LH. In sheep and rats, inhibin B suppresses FSH synthesis and secretion (25,26).…”

Soybean isoflavone exposure does not have feminizing effects on men: a critical examination of the clinical evidence

“…Furthermore, proponents of this hypothesis primarily cite in utero and infancy as the key exposure periods for effects to occur (9,22,140). Hypothyroidism can adversely affect spermatogenesis (141), but because only morphology is affected and, as noted previously, there is essentially no evidence that soy adversely affects thyroid function in healthy individuals, no further comment about this relationship will be made (116).…”

Is there a role for thyroid hormone on spermatogenesis?

“…Nevertheless, TRs were also identified in spermatogenic germ cells undergoing differentiation, suggesting a possible role for thyroid hormone in normal spermatogenesis and metabolism in the adult testis. Although studies that have specifically focused on thyroid hormone effects in spermatogenesis are by far limited, some recent reports have demonstrated that altered thyroid status in adult males is associated with abnormal spermatogenesis in animals and humans (Faraone-Mennella et al, 2008;Krassas and Pontikides, 2004;Krassas et al, 2008a;Meeker et al, 2007;Weng et al, 2007). Although, collectively, these results suggest that thyroid hormone might play a role in the endocrine regulation of spermatogenesis, the potential biological importance of TRs in germ cells remains to be established.…”