Effect of Thyroid Hormone Derangements on Sexual Function in Men and Women

As a consequence, SHBG, total, and free testosterone concentrations are decreased 22 (Fig.2). Krassas et al. have demonstrated that patients affected by hypothyroidism show more frequently atypical sperm percentage than euthyroid patients 90. Moreover, they have found a correlation between teratozoospermia and fT4 levels 90, with an improvement in spermatozoa morphology after replacement treatment 90. Hypothyroidism may also decrease the total sperm number and motility as well as lead to an impairment in acrosome integrity and mitochondrial activity 108, with improved motility upon hormone replacement 89, 109 (Fig. 2). To this regard, Thangaratinam et al. 57 reported an odds ratio (OR) of miscarriage of 3.15 while Busnelli et al. an OR of 1.44 58.

A rare cause of hyperthyroidism in pregnancy is the mutation of the TSH receptor gene with functional hypersensitivity to hCG. Due to the stimulating effect of hCG on TSH receptor, serum TSH may decrease in the first trimester, with a peak of hCG between 7- and 11-weeks’ gestation. Even TSH levels lower than synthroid goitrogens 0.1 mU/L may occur approximately in 5% of women by week 11 of pregnancy 9. In conclusion, normal putative thyroid activity seems a requisite for male reproductive functions. However, the knowledge about the interaction between the two classical endocrine axes, hypothalamo-hypophyseal-testicular axis and hypothalamo-pituitary-thyroid axis, is still rudimentary and needs further investigation. To confirm the role of TSH further we recruited normal men with TSH values 1.75 ± 0.82μIU/ml and men with low TSH, mean values 0.13 ± 0.12μIU/ml (Reference range of TSH 0.35–4.94μIU/ml) and normal T3 and T4.

Most of the studies on the effect of thyroid hormones on male fertility were conducted between the years 1970 and 2000 (1). The effects of thyroid hormone alterations on the reproductive system have been studied extensively in human subjects and animal models that have generally shown that changes from normal thyroid function resulted in decreased sexual activity and fertility (2, 3). The underlying mechanisms, however, are not constant throughout all species, and results from different studies disagree (4).

Thyroid Hormones and Spermatozoa: In Vitro Effects on Sperm Mitochondria, Viability and DNA Integrity

Interestingly, the beneficial impact may be only for those conceiving naturally, as the miscarriage rate was unchanged in those undergoing ART 63. Stagnaro-Green for the first time showed an association between pregnancy loss and thyroid autoimmunity, thus the patients who were positive for TAI demonstrated a twofold increased risk of pregnancy loss 65, data later confirmed by several other studies and meta-analyses 66–70. Women with normal thyroid function positive for TPOAb or TgAb also seem to have a significantly higher risk of preterm birth, reaching an OR as high as 2.9, as reported by several large studies and meta-analyses 57, 71–74.

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Regular thyroid function tests should be an essential part of any fertility evaluation, especially in cases of unexplained infertility. By identifying subclinical hypothyroidism or other thyroid disorders early, men can benefit from treatments like thyroid hormone replacement therapy and improve their reproductive health. Hyperthyroidism, an overproduction of thyroid hormones, can reduce semen volume, cause abnormal sperm morphology and lower sperm motility. Thankfully, with the right thyroid medication and management, these thyroid problems can often be corrected, improving semen quality. Two genes (TRα and TRβ) encode five isoforms thatare obtained by alternate splicing (TRα1, TRα2, TRα3, TRβ1, and TRβ2).

Hypothyroidism

Antithyroid drugs are best taken in smaller doses over two or three times a day following a feed. If you require higher doses of antithyroid drugs to control hyperthyroidism then your baby can have a blood test to check whether its thyroid is being affected. An important role in the central and peripheral crosstalk is also played by adipokines; specifically, kisspeptin, which is essential for human reproduction acting on the hypothalamus and stimulating GnRH production, may also stimulate TSH 10.

Your thyroid gland

Altered redox status of the testis, Sertoli cells and Leydig cells in hyperthyroidism, such as decreased glutathione peroxidise activities, also affect the quality of semen. Sperm motility may also be hindered in hyperthyroidism via impairment of mitochondrial activities in spermatozoa. Thus, reduced sperm count, vitality, and motility ultimately suggest a decline in semen quality owing to hyperthyroidism.

This review also highlights the limitations of the studies carried out so far and accentuates the necessity of large-scale human studies and animal studies specifically focusing on the molecular events of thyroid disorder-induced alterations in semen quality. In hypothyroidism, decreased circulating T3 and T4 levels, reduced SHBG concentrations, decreased serum testosterone level adversely affect spermatogenesis. Hypothyroidism is also characterized by a decrease in seminiferous tubular diameter and reduction in testicular, epididymal and prostate weight thus affecting sperm development, progressive sperm motility, sperm transit time through the epididymis.

Identifying these conditions early through a thyroid function test is essential, as effective management can greatly improve both male fertility and overall well-being.
A meta-analysis investigating the effect of levothyroxine treatment in TAI-positive women undergoing ART denied any positive impact on that the miscarriage rate; however, levothyroxine decreased the miscarriage rate if subclinical hypothyroidism was present 63 suggesting that this condition per se may be detrimental 9, 64.
In this review we explore the impact of thyroid dysfunction on female and male sexual function.
Thus, in patients with hypothyroidism, increased testicular size is observed along with a significant drop in mature germ cells within the seminiferous tubules (22, 23).

Not only SHBG, but also other hormone binding proteins, such as corticosteroid-binding globulin (CGB) and thyroglobulin-binding-protein (TBG), are an index of thyroid action on the liver 24. In addition, prolonged hyperthyroidism leads to direct liver toxicity and hepatocyte anoxia with impaired liver function 26. The most common cause of thyrotoxicosis, a clinical syndrome resulting in exposure to thyroid hormone excess, is hyperthyroidism, which, in reproductive age, is usually due to autoimmune Graves’ disease (GD). It is crucial to differentiate it from relatively common, hyperemesis gravidarum, which occurs in 0.3–1% of the cases.

Clyde et al. by studying individual cases reported adverse effects of hyperthyroidism on semen quality (26).
Some patients have TSH concentrations that are raised above the normal reference range with free thyroxine (fT4) in the normal reference range.
The rise in LH was not as high as seen in cycling females which could result due to high testosterone levels Figure 3.66 Boucekkine and Semrouni (1990)69 examined the effect of estradiol on basal and GnRH – stimulated gonadotropin secretion in patients with Klinefelter’s syndrome.
To confirm the role of TSH further we recruited normal men with TSH values 1.75 ± 0.82μIU/ml and men with low TSH, mean values 0.13 ± 0.12μIU/ml (Reference range of TSH 0.35–4.94μIU/ml) and normal T3 and T4.
Probably, this is because patients with hyperthyroidism should postpone IVF techniques after normalization of thyroid function 27.

Thyroid function tests

Given these data, it is not difficult to imagine that an altered thyroid functionaffects spermatogenesis and therefore semen quality.3,4 Most of the studies mentioned inthis article have been carried out in mice/rats and subsequently in humans. After the birth you will probably need to return to the dose of levothyroxine you were taking before the pregnancy. You should have a blood test to check your thyroid hormone levels a few weeks after the birth.