What does the thyroid gland located in your neck have to do with your periods, ovulation, fertility, and pregnancy? The hormones that are made by the thyroid gland like T4 and T3 are absolutely necessary for hormone harmony in the rest of your body.
Hypothyroidism and Fertility
What does the thyroid gland located in your neck have to do with your periods, ovulation, fertility, and pregnancy? The hormones that are made by the thyroid gland like T4 and T3 are absolutely necessary for hormone harmony in the rest of your body. When these levels become too low, it’s like throwing a wrench in your hormonal machine.
So, what exactly, can a low thyroid do to your well thought out fertility plans? It turns out, a whole bunch:
- Makes your periods heavier. Balanced thyroid hormones are needed in order to stimulate the ovary to make the right amounts of estrogen and progesterone. Without the ideal amounts of estrogen and progesterone hanging around, periods become heavier. [2], [3].
- Prevents implantation. Hypothyroidism often coexists with low progesterone which is the key player in helping the egg to “stick” to the wall of the uterus (implantation). When Progesterone is low, the egg isn’t able to implant. Hypothyroidism is one of the causes for a miscarriage that occurs early on in pregnancy. [5]
- Shortens pregnancy by reducing the mother’s ability to carry the baby the entire 40 weeks. Hypothyroid is associated with preterm birth, or a baby born before their due date. [1]
- Affects the baby’s growth. Hypothyroidism can interfere with the baby’s development too while they are still trying to grow in the womb. [6]
Unfortunately, just because your TSH is normal doesn’t mean you are safe. The presence of thyroid specific antibodies like TPO Antibodies and Thyroglobulin antibodies can prevent fertilization, implantation, and are associated with early miscarriage. [4]. Some estimates suggest that miscarriage is twice as likely when thyroid antibodies are present.[4]
Whether you’re just starting out in your fertility journey, you've been hard at work for a while, or you're recovering from miscarriage, the role of your thyroid gland is intertwined to all aspects of reproductive health and should be part of your fertility workup.
References:
- Abalovich M, Gutierrez S, Alcaraz G, Maccallini G, Garcia A, Levalle O. Overt and subclinical hypothyroidism complicating pregnancy. Thyroid. 2002 Jan;12(1):63-8. doi: 10.1089/105072502753451986. PMID: 11838732.
- Ajmani NS, Sarbhai V, Yadav N, Paul M, Ahmad A, Ajmani AK. Role of Thyroid Dysfunction in Patients with Menstrual Disorders in Tertiary Care Center of Walled City of Delhi. J Obstet Gynaecol India. 2016 Apr;66(2):115-9. doi: 10.1007/s13224-014-0650-0. Epub 2015 Jan 20. PMID: 27046965; PMCID: PMC4818825.
- Kalyani P. Menstrual irregularities in hypothyroidism. Journal of Evolution of Medical and Dental Sciences. 2015 Jan 29;4(9):1522-8.
- Negro R. Levothyroxine before conception in women with thyroid antibodies: a step forward in the management of thyroid disease in pregnancy. Thyroid Res. 2019 Jun 20;12:5. doi: 10.1186/s13044-019-0066-0. PMID: 31249628; PMCID: PMC6585063.
- Ren B, Zhu Y. A New Perspective on Thyroid Hormones: Crosstalk with Reproductive Hormones in Females. International Journal of Molecular Sciences. 2022; 23(5):2708. https://doi.org/10.3390/ijms23052708
- 18, Stagnaro-Green A, Roman SH, Cobin RH, el-Harazy E, Alvarez-Marfany M, Davies TF. Detection of at-risk pregnancy by means of highly sensitive assays for thyroid autoantibodies. JAMA. 1990 Sep 19;264(11):1422-5. PMID: 2118190.