A link between hypothyroidism, obesity and male reproduction

Abstract

Hypothyroidism is a condition in which the serum levels of thyroid hormones are below that necessary to carry out physiological functions in the body. Hypothyroidism is related to obesity as an increase in body weight gain is seen in hypothyroid patients. Moreover, an inverse correlation between free thyroxine values and body mass index has been reported. Leptin, a polypeptide hormone produced by adipocytes, was originally thought to be an antiobesity hormone due its anorexic effects on hypothalamic appetite regulation. However, nowadays it is known that leptin conveys information about the nutritional status to the brain being considered a crucial endocrine factor for regulating several physiological processes including reproduction. Since the identification of thyroid hormone and leptin receptors on the testes, these hormones are being recognized as having important roles in male reproductive functions. A clear link exists among thyroid hormones, leptin and reproduction. Both hormones can negatively affect spermatogenesis and consequently may cause male infertility. The World Health Organization (WHO) estimates the overall prevalence of primary infertility ranging from 8 to 15%. The fact that 30% of couples' inability to conceive is related to a male factor and that the longer hypothyroidism persisted, the greater the damage to the testes, strongly suggest that more studies attempting to clarify both hormones actions directly in the testes need to be conducted specially in cases of congenital hypothyroidism. Therefore, the goal of this review is to highlight the relationship of such hormones in the reproductive system.

Protective Effects of Fluvastatin on Reproductive Function in Obese Male Rats Induced by High-Fat Diet through Enhanced Signaling of mTOR

“…This is not only associated with a variety of chronic diseases, such as hyperlipidemia, diabetes mellitus, hypertension, but has also been demonstrated to have hazardous effects on the reproductive system and fertility [2][3][4][5]. Moreover, obesity can affect male infertility by affecting spermatogenesis, thus reducing fertilization rate [5][6][7][8][9].…”

Examining the Effects of Ikmo (Piper Betle Linn.) on the Thyroxine Level of Female Albino Rats and Its Relationship to Infertility and Hyperprolactinemia

“…One study 23 reported that thyroid disease negatively affects spermatogenesis and consequently may cause male infertility. Decreased libido or impotence is also present in hypothyroidism 24 .…”

Altered sperm parameters and subclinical hypothyroidism; A cross sectional study in Karachi, Pakistan

“…is alteration in thyroid hormone (TH) levels. 4 TH has long been established as a factor affecting testicular development with associated reproductive functions, particularly during the prepubertal period. 4 These effects are manifested by the effect of TH on Leydig, Sertoli and germ cells disturbing erectile functions and sperm parameters (count, morphology and motility; both progressive and non-progressive).…”

“…4 TH has long been established as a factor affecting testicular development with associated reproductive functions, particularly during the prepubertal period. 4 These effects are manifested by the effect of TH on Leydig, Sertoli and germ cells disturbing erectile functions and sperm parameters (count, morphology and motility; both progressive and non-progressive). 5,6 Hypothyroidism in particular increases the sperm transit time through the epididymis, which causes a reduction in total and daily sperm productions.…”

“…5 It reduces serum testosterone levels and is associated with hypogonadism and sperm morphological abnormalities. 4,7 More recent studies, however, have shown that hypothyroidism causes decreased total testosterone (TT) and "sex hormone binding globulin (SHBG)" levels, whereas "luteinizing hormone (LH)"…”