Clinical implications of altered thyroid status in male testicular function

Abstract

Thyroid hormones are involved in the development and maintenance of virtually all tissues. Although for many years the testis was thought to be a thyroid-hormone unresponsive organ, studies of the last decades have demonstrated that thyroid dysfunction is associated not only with abnormalities in morphology and function of testes, but also with decreased fertility and alterations of sexual activity in men. Nowadays, the participation of triiodothyronine (T3) in the control of Sertoli and Leydig cell proliferation, testicular maturation, and steroidogenesis is widely accepted, as well as the presence of thyroid hormone transporters and receptors in testicular cells throughout the development process and in adulthood. But even with data suggesting that T3 may act directly on these cells to bring about its effects, there is still controversy regarding the impact of thyroid diseases on human spermatogenesis and fertility, which can be in part due to the lack of well-controlled clinical studies. The current review aims at presenting an updated picture of recent clinical data about the role of thyroid hormones in male gonadal function. RESUMOOs hormônios da tireoide estão envolvidos virtualmente no desenvolvimento e na manutenção de todos os tecidos. As gônadas masculinas foram, por décadas, consideradas insensíveis aos hormônios tireoidianos. No entanto, estudos mais recentes têm demonstrado que disfunções tireoidianas estão associadas não somente a anormalidades na morfologia e na função dos testículos, mas também à diminuição da fertilidade e alterações na atividade sexual masculina. Atualmente, o papel da triiodotironina (T3) no controle da proliferação das células de Sertoli e Leydig, maturação testicular e esteroidogênese é amplamente aceito, bem como a presença de transportadores e receptores para o hormônio tireoidiano nos testículos durante o período de desenvolvimento e a idade adulta. No entanto, apesar dos dados que indicam que o T3 atua diretamente nos testículos humanos, persistem controvérsias em relação ao impacto das doenças tireoidianas sobre a espermatogênese e a fertilidade, o que pode ser em parte devido à escassez de estudos clínicos nessa área. Essa revisão tem por objetivo apresentar um panorama de dados clínicos atualizados sobre o papel dos hormônios tireoidianos na função gonadal masculina. Arq Bras Endocrinol Metab. 2009;53(8):976-82 Descritores

Effects of hyper‐ and hypothyroidism on the development and proliferation of testicular cells in prepubertal rats

“…Moreover, the some study suggests that thyroid hormones have direct effect on gonadotropin sensitivity to gonadotropin‐releasing hormone, which may lead to disturbance in the production of LH and FSH; due to this disorder hyperthyroidism causes improper erection and spermatogenetic dysfunction in men (Wajner et al . ).…”

Experimentally induced hyperthyroidism influences oxidant and antioxidant status and impairs male gonadal functions in adult rats

“…Moreover, evidences from experimental studies in male rats suggest an important role of THs in reproductive failure (Cooke & Meisami, 1991). Clinical literature indicates that most patients with THs disorders experience some kind of sexual dysfunction, which improves or normalises when patients become euthyroid (Carani et al, 2005;Wajner et al, 2009). Furthermore, changes in THs level during early testicular development have been shown to affect testicular maturation and reproduction later in life (Wagner et al, 2008).…”

Association of subclinical hypothyroidism and phenotype, insulin resistance, and lipid parameters in young women with polycystic ovary syndrome

“…It is also known to affect gonadal function, puberty, and fertility and may also lead to the PCOS type of phenotypic expression (11)(12)(13). For this reason all the existing criteria used for diagnosis of PCOS necessitate exclusion of hypothyroidism at first (14)(15)(16).…”