Thyroid and Fertility Relationship

The thyroid gland may be small, but it has a major influence on multiple processes in our body in both direct and indirect manner. The thyroid produces hormones that regulate metabolism, manage our weight, and so much more.

Hormonal balance is vital for good health and wellbeing.  Bearing in mind thyroid has such a meaningful impact on our overall health and sex hormones it’s impossible not to wonder if this gland also affects fertility in any way. We bring you all the answers below.

How common are fertility struggles?

Many couples struggle to conceive and the term “infertility” is used whenever pregnancy doesn’t occur. However, infertility is defined as not being able to get pregnant, despite making efforts, for a year or longer according to the CDC.

Women are considered infertile if they are unable to get pregnant after six months.

Although every man or woman who goes through fertility issues thinks others don’t face the same problem, figures show the opposite.

About 6% of married women aged 15-44 are unable to get pregnant after one year of trying. In addition, 12% (7.4 million) women are unable to get or stay pregnant regardless of the marital status.

In 35% couples with infertility, a male factor is identified together with the female factor. For 8% of cases, male infertility is the only identifiable cause[1]. Numerous factors play a role in fertility of both men and women. Below, we discuss the role of the thyroid.

Hyperthyroidism and fertility

Hyperthyroidism or overactive thyroid is a condition wherein the gland produces excessive levels of the hormone thyroxine. The condition accelerates a person’s metabolism and causes a number of symptoms such as sudden weight loss, sweating, rapid heartbeat, increased sensitivity to heat, skin dryness, mood swings, and many others[2].

The condition is ten times more prevalent among women than in men[3]. Individually or in combination, symptoms of hyperthyroidism can contribute to infertility.

Besides common symptoms mentioned above, hyperthyroid women can deal with irregular periods which make the conception a lot more difficult.

The negative influence of hyperthyroidism on fertility was confirmed by scientific research. Jefferys et al carried out a study whose primary goal was to evaluate the impact of thyroid on fertility. They found that 2.3% of women with fertility problems had overactive thyroid i.e. hyperthyroidism compared to 1.5% of those in general population[4].

How does hyperthyroidism affect fertility?

The study explains it could be down to increased sensitivity to gonadotrophin-releasing hormone or GnRH (controls the production of luteinizing and follicle stimulating hormones from the pituitary) which increases levels of luteinizing hormone and sex hormone-binding globulin.

The result is a rise in estrogens. Estrogen dominance can cause many conditions affecting fertility including polycystic ovarian syndrome (PCOS).

Even though women are more prone to hyperthyroidism and other thyroid disorders men can develop them too. Overactive thyroid affects male fertility as well. Clyde et al looked at three individual case studies of hyperthyroid men and infertility.

It was concluded that male infertility is more common than previously thought in males with hyperthyroidism and it’s probably in correlation with elevated levels of luteinizing hormones (LH), testosterone, and follicle stimulating hormone (FSH)[5]. The study also showed that quality of semen decreased as well.

Hudson and Edwards discovered that hyperthyroidism affects spermatogenesis by altering sex steroid levels[6].

This shows that excessive production of thyroid hormones has a negative impact on levels of testosterone and other hormones and it impairs spermatogenesis (production or development of mature spermatozoa). As a result, the condition affects male fertility too.

Hypothyroidism and fertility

Hypothyroidism is a common thyroid disorder indicated by the insufficient production of thyroid hormones.

The condition is characterized by symptoms such as weight gain, high cholesterol, fatigue, hair loss, and others. Just like hyperthyroidism, this condition is also more prevalent in women than in men and it can affect one’s fertility.

Verma et al investigated the prevalence of hypothyroidism among infertile women and response to treatment for hypothyroidism on fertility.

Of 394 infertile women who participated in the study, 23.9% were hypothyroid. Fortunately, after treatment for hypothyroidism, 76.6% of infertile women managed to conceive within six weeks to one year.

Hypothyroidism is strongly linked to increased production of TRH (thyrotropin-releasing hormone) which goes on to stimulate the pituitary gland to elevate secretion of TSH and prolactin (PRL).

This can lead to hyperprolactinemia, a condition of elevated prolactin. Hyperprolactinemia adversely affects fertility by disrupting pulsatility of GnRH and ovarian function[7]. At this point, the egg is not released during ovulation or it is released irregularly and a woman experiences difficulty conceiving.

Jefferys et al who published a study that confirmed the relationship of hyperthyroidism and infertility also explored the role of hypothyroidism.

The condition is common and findings show that 0.5% women of reproductive age have overt hypothyroidism. The underactive thyroid is known to affect the pulsatile release of GnRH which is vital for the cyclical release of FSH, LH, and subsequent ovulation.

The study also showed that thyroid hormone receptors are also expressed by ovarian granulosa cells, oocytes, and cumulus cells and they participate in activation of LH receptors and production of progesterone.

In addition, hypothyroidism changes feedback to the pituitary through altered metabolism of estrogen and circulating levels of sex hormone-binding globulin (SHBG). Similarly to hyperthyroidism, this condition affects menstrual cycle as well and it is yet another mechanism behind its negative effect on fertility.

For example, hypothyroidism can shorten the menstrual cycle which may not allow a fertilized egg enough time to attach to the womb. As you can easily conclude, this affects fertility too.

Elevated levels of TSH could be linked to decreased rates of fertilization during assisted conception and reduced pregnancy rates among ladies with a serum TSH of 2.5mU/l or more4.

Not only does hypothyroidism affect female fertility, but male as well. Krassas and Perros found that underactive thyroid may lead to a decrease in the levels of SHBG and a reduction in total serum testosterone levels[8].

Hypothyroid men also have lower levels of LH and FSH. That said, effects of hypothyroidism on male fertility are less severe than those associated with hyperthyroidism[9].

Krassas carried out a separate study which found that hypothyroidism adversely affects human spermatogenesis. Both morphology and motility of sperm are affected[10].

 

Thyroid autoimmunity and fertility

Thyroid autoimmunity is the most common cause of thyroid disorders.

Hashimoto’s thyroiditis is the most common cause of hypothyroidism while Graves’ disease causes hyperthyroidism. Thyroid autoimmunity occurs when the body’s immune system starts attacking healthy cells and tissues, in this case, thyroid.

Women with thyroid autoimmunity can experience fertility problems too. Poppe et al found that prevalence of thyroid autoimmunity is significantly higher in infertile women than their fertile counterparts. Although having an autoimmune thyroid condition does not interfere with normal embryo implantation, the risk of miscarriage in early stages of pregnancy is high[11].

The connection between thyroid autoimmunity, endometriosis, and ovarian failure has been identified in some studies. Endometriosis is a condition that occurs when bits of the tissue that lines the uterus (endometrium) grow on the pelvic organs like fallopian tubes and ovaries.

The condition has been an association with various immunological changes such as the presence of autoantibodies to endometrial antigens, the decline in the concentration of natural killer cells, complement deposits, among others[12].

Weight changes

Both hyperthyroidism and hypothyroidism have a major influence on your weight. While hypothyroidism can cause weight gain, persons with hyperthyroidism tend to lose weight without even trying to do so.

A person’s weight can affect fertility. This means that thyroid function can have both direct and indirect impact on your fertility and likelihood to conceive. Jokela et al discovered that obese women and men and underweight men are less likely to have as many children in adulthood as they had desired as young adults[13].

Other studies also demonstrate that prevalence of infertility in obese women is high. In fact, most women who seek treatment for infertility tend to be overweight or obese. Weight loss poses a useful strategy to increase fertility potential[14].

Low libido

In order to conceive, couples need to have regular sex, particularly during ovulation.

Sexual desire is necessary for intercourse, otherwise, it would appear mechanic. When a person doesn’t feel the desire to have sex, they won’t have it. Multiple factors play a role in libido, and your thyroid is one of them.

Oppo et al investigated sexual function in hyper- and hypothyroid women prior to and immediately after restoration of euthyroidism and in ladies with euthyroid Hashimoto’s thyroiditis. They enrolled 46 women with thyroid diseases and 30 age-matched healthy women.

Scientists discovered that hypo- and hyperthyroid women experienced reduced scores in all sexual domains.

Treatment of hypothyroidism normalized sexual satisfaction, libido, and pain. On the other hand, hyperthyroid women experienced improvement in sexual desire, arousal, lubrication, pain, and satisfaction after treatment for their condition[15].

These findings confirm that thyroid disorders have a significant influence on libido. This can lead to loss of interest in sex. Reduced frequency of intercourse is bad news for couples who want to get pregnant.

A longer examination of the relationship between libido and the thyroid can be found here.

Improving your fertility

Fertility struggles aren’t uncommon, most couples experience them. Difficulty conceiving doesn’t automatically indicate your chances of having a baby are reduced to zero. Many men and women experience the same problems and overcame them successfully.

Sure, thyroid problems make the process more difficult, but it’s not impossible. Below, you can see different things you can do to improve your fertility:

  • Get thyroid hormone levels tested – different factors affect fertility, not just estrogen and testosterone. Couples, especially women, who experience difficulties to get pregnant should get their thyroid hormone levels checked. Based on the lab results, the doctor can determine whether thyroid dysfunction plays the role. Management of the underlying problem boosts your fertility potential. Our guide to improving thyroid function can be found here.
  • Keep weight in a healthy range – as seen above, thyroid affects your weight and it’s important to keep it in a healthy range. Healthy weight is important for hormonal balance, better fertility, and prevention of diabetes, heart disease, you name it
  • Track your menstrual cycle – this is an easy way to spot any irregularities which could also be tied to thyroid problems
  • Have sex – couples can benefit from sex schedules, particularly at peak of fertility
  • Exercise regularly – physical activity is of huge importance for overall health and wellbeing. Not only it helps manage your weight, but it boosts energy levels. This is particularly important for hypothyroid men and women because the condition is associated with fatigue. Physical activity can also increase libido and contribute to hormone balance

Conclusion

Thyroid function affects fertility in many ways. Both hypothyroidism and hyperthyroidism can affect fertility potential of both men and women.

Thyroid autoimmunity can also contribute to infertility. Treatment of thyroid disorders can improve fertility and increase the chances of getting pregnant.

It is important for men and women to get their thyroid levels tested if they experience difficulties getting pregnant.

References

[1] Infertility FAQs, CDC https://www.cdc.gov/reproductivehealth/infertility/index.htm

[2] Hyperthyroidism overview, Endocrine Web https://www.endocrineweb.com/conditions/hyperthyroidism/hyperthyroidism-overview-overactive-thyroid

[3] Vanderpump MP, Tunbridge WM, French JM, et al. The incidence of thyroid disorders in the community: a twenty-year follow-up of the Whickham Survey. Clinical Endocrinology Jul 1995;43(1):55-68 https://www.ncbi.nlm.nih.gov/pubmed/7641412

[4] Jefferys A, Vanderpump M, Yasmin E. Thyroid dysfunction and reproductive health. The Obstetrician and Gynecologist 2015 Jan;17(1):39-45. Doi: 10.1111/tog.12161 http://onlinelibrary.wiley.com/doi/10.1111/tog.12161/full

[5] Clyde HR, Walsh PC, English RW. Elevated plasma testosterone and gonadotropin levels in infertile males with hyperthyroidism. Fertility and Sterility 1976 Jun;27(6):662-6 https://www.ncbi.nlm.nih.gov/pubmed/946959/

[6] Hudson RW, Edwards AL. Testicular function in hyperthyroidism. Journal of Andrology, 1992 Mar-Apr;13(2):117-24 https://www.ncbi.nlm.nih.gov/pubmed/1597395/

[7] Verma I, Sood R, Juneja S, Kaur S. Prevalence of hypothyroidism in infertile women and evaluation of response of treatment for hypothyroidism on infertility. International Journal of Applied and Basic Medical Research. 2012;2(1):17-19. doi:10.4103/2229-516X.96795. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3657979/

[8] Krajewska-Kulak E, Sengupta P. Thyroid Function in Male Infertility. Frontiers in Endocrinology. 2013;4:174. doi:10.3389/fendo.2013.00174. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3826086/

[9] Krassas GE, Perros P. Thyroid disease and male reproductive function. Journal of Endocrinological Investigation 2003 Apr;26(4):372-80. Doi: 10.1007/BF03345187 https://www.ncbi.nlm.nih.gov/pubmed/12841547/

[10] Krassas GE, Papadopoulou F, Tziomalos K. Hypothyroidism has an adverse effect on human spermatogenesis: a prospective, controlled study. Thyroid 2008 Dec;18(12):1255-9. Doi: 10.1089/thy.2008.0257 https://www.ncbi.nlm.nih.gov/pubmed/19012472/

[11] Poppe K, Velkeniers B, Glinoer D. The role of thyroid autoimmunity in fertility and pregnancy. Nature Clinical Practice: Endocrinology and Metabolism 2008 Jul;4(7):394-405. Doi: 10.1038/ncpendmet0846 https://www.ncbi.nlm.nih.gov/pubmed/18506157

[12] Thyroid disorders associated with infertility and pregnancy, Medscape https://www.medscape.org/viewarticle/574861_4

[13] Jokela M, Elovainio M, Kivimaki M. Lower fertility associated with obesity and underweight: the US National Longitudinal Survey of Youth. American Journal of Clinical Nutrition 2008 Oct;88(4):886-893. http://ajcn.nutrition.org/content/88/4/886.full

[14] Dağ ZÖ, Dilbaz B. Impact of obesity on infertility in women. Journal of the Turkish German Gynecological Association. 2015;16(2):111-117. doi:10.5152/jtgga.2015.15232. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4456969/

[15] Oppo A, Franceschi E, Atzeni F, et al. Effects of hyperthyroidism, hypothyroidism, and thyroid autoimmunity on female sexual function. Journal of Endocrinological Investigation 2011 Jun;34(6):449-53. Doi:10.1007/BF03346712 https://www.ncbi.nlm.nih.gov/pubmed/21532331

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