Does thyroid function affect fertility?

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Can thyroid function cause infertility or recurrent miscarriage?


Hormonal testing that is part of a typical fertility evaluation includes screening for thyroid dysfunction. Overactive or underactive thyroid function can lead to issues with fertility and increased risks in pregnancy, specifically miscarriage.

The typical screening test for thyroid is thyroid-stimulating hormone (TSH) and the results can be confusing since a high TSH is a sign of an underactive thyroid gland.

TSH is the hormone released from the pituitary gland and tells the thyroid to make or not make thyroid hormone. If the thyroid is not making enough thyroid hormone the TSH will be high.

The level of TSH optimal for fertility and in pregnancy can be controversial but the Endocrine Society states higher risk women (those with infertility and recurrent miscarriage) should have a tighter control of thyroid before and during pregnancy (usually <2.5 mIU/L).

Demand on the thyroid increases by 30% in the first trimester of since the baby does not make it’s own thyroid hormones until about 10 weeks of pregnancy.

Hypothyroidism (underactive thyroid, low thyroid, high TSH) has been associated with an increased risk of miscarriage.

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About the Author:

Lora Shahine, MD, FACOG is a board-certified reproductive endocrinologist currently practicing at Pacific NW Fertility and IVF Specialists in Seattle. Dr. Shahine is an accomplished author of many blogs and articles as well as three books. Her first book, “Planting the Seeds of Pregnancy: An Integrative Approach to Fertility Care” she co-authored a guide to both Eastern and Western approaches to fertility care. Her second book, “Not Broken: An Approachable Guide to Miscarriage and Recurrent Pregnancy Loss” is an evidence-based review of the current evaluation and treatment for miscarriage. Most recently, she published “Not Broken Illustrated: A Gift for Those Who Have Suffered Pregnancy Loss.” She is dedicated to changing the conversation surrounding infertility and miscarriage from one of shame and guilt to one of support and empowerment.

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