Struggling to conceive? Expert reveals link between hypothyroidism and infertility

For women trying to conceive, thyroid function is one of the more frequently overlooked variables in the fertility picture. In India, a study in the Indian Journal of Endocrinology and Metabolism estimates that 1 in 10 women has some form of thyroid dysfunction. Many of them are actively trying to conceive without knowing that their thyroid is working against their efforts. Understanding what hypothyroidism does to the reproductive system, and what can be done about it, changes the clinical approach significantly.

How does hypothyroidism affect fertility?

The thyroid’s influence on reproductive function runs deeper than most women expect. Hypothyroidism contributes to infertility by disrupting multiple reproductive processes, including follicular development, fertilisation, embryo implantation, and hormonal regulation. The condition affects the secretion of key reproductive hormones, including thyrotropin-releasing hormone, prolactin, gonadotropin-releasing hormone, follicle-stimulating hormone, and luteinising hormone, thereby compromising normal reproductive function through multiple pathways.

The practical consequences of this hormonal disruption are visible in the menstrual cycle. Low thyroid hormone disrupts the hypothalamic-pituitary-ovarian axis, meaning the brain does not send the right signals to the ovaries. Cycles become longer, unpredictable, or disappear entirely. Even when periods are regular, ovulation may not occur, and without ovulation, conception is not possible.

Women with hypothyroidism may have an infertility rate of up to 30 per cent, compared to 10 to 15 per cent in women with normal thyroid function, as per the Journal of Clinical Medicine Research. These are not marginal differences. They reflect the significant reproductive load that inadequately managed thyroid dysfunction places on the body.

What should your TSH level be when trying to conceive?

One of the more important clinical distinctions for women trying to conceive is the difference between a thyroid result that is normal by standard laboratory criteria and one that is optimised for fertility. Standard TSH reference ranges in most laboratories extend to 4.5 or 5 mIU/L. For women trying to conceive or undergoing fertility treatment, most specialists work to a tighter target, generally below 2.5 mIU/L, because TSH levels in the higher end of the normal range can still interfere with ovulation and implantation even when they do not meet the threshold for a clinical hypothyroidism diagnosis.

Women with known hypothyroidism treated with levothyroxine before conception should plan to increase their dosage by 25 to 50 per cent in the first trimester, as per the British Journal of General Practice, reflecting how significantly pregnancy increases the thyroid’s workload. This adjustment needs to be planned before conception, not after a positive pregnancy test.

What do women with hypothyroidism do?

For women trying to conceive with a known hypothyroidism diagnosis, the most direct intervention is optimising TSH to the fertility-specific target under the guidance of an endocrinologist or fertility specialist. With six weeks to one year of appropriate thyroid treatment, 76.6 per cent of infertile women with hypothyroidism achieved conception, which reflects how responsive fertility can be to adequate thyroid management as per the International Journal of Applied & Basic Medical Research.

Beyond medication, thyroid antibody status should be assessed. Women with elevated thyroid peroxidase antibodies carry a higher risk of miscarriage and pregnancy complications even when TSH is within the normal range. Identifying antibody positivity before conception allows for closer monitoring and more proactive management during early pregnancy.

You may also like

Hepatitis Awareness: How to prevent mother-to-child transmission of Hepatitis Watch Video

Common myths about pap smears that stop women from getting screened Read Article

Lifestyle factors, including selenium-rich foods, adequate iodine intake, and stress management, all support thyroid function. They are not substitutes for medical management, but they contribute to the overall hormonal environment in which conception occurs.

When to see a fertility specialist?

Women with hypothyroidism who have been trying to conceive for six months or more without success warrant a full fertility evaluation rather than continued optimisation of thyroid function alone. Thyroid dysfunction frequently coexists with other fertility factors, including PMOS, diminished ovarian reserve, and uterine abnormalities. Addressing thyroid health is an important part of the picture. Still, a complete assessment ensures that nothing else is being missed while time passes.