The prevalence of thyroid autoimmunity and subclinical hypothyroidism is significant among women of reproductive age. It is estimated that the incidence of autoimmune thyroid disease is 8-14 percent and is the most common cause of hypothyroidism among young women. The high prevalence of this condition makes it an important health concern, especially when a woman is considering pregnancy.
A Quick Breakdown
How does the thyroid work? The hypothalamus, a small organ in the brain, secretes Thyroid Releasing Hormone (TRH), which signals the pituitary gland to secrete Thyroid Stimulating Hormone (TSH). TSH then signals the thyroid gland, located in the front of the neck to secrete thyroid hormone. These hormones are named T4 and T3 and are released into the blood at a ratio of 20 to 1. T3 is the active hormone, meaning it is the one that does all the work. T4 is converted to T3 in the liver and other parts throughout the body.
Important enzymes are needed for certain actions to occur; these include thyroid peroxidase and deiodinases. Thyroid peroxidase is needed to convert ingested iodine to a usable form in the body and deiodinases are needed to convert T4 to active T3. Selenium, iron, zinc, and iodine are all essential nutrients the body needs for the proper function of all processes in the thyroid hormone cycle.
Why is adequate thyroid hormone so important to our reproductive health?
Thyroid hormone is essential for life. It stimulates the growth of tissues and controls metabolic rate and heat production. A fetus depends on the mother’s T4 hormone for the first 24 weeks, a little over half of the pregnancy term. The fetal brain develops rapidly between weeks 12 and 22 of gestation, which means that optimal T4 hormone from the mother is essential for fetal brain development.
Hypothyroidism is defined as a high TSH and low T4. Subclinical hypothyroidism is defined as a high TSH and a T3 within normal range. Thyroid autoimmunity is defined when auto-antibodies against the enzyme thyroid peroxidase (TPO-Ab) and/or thyroglobulin (Tg-Ab) are present in the blood.
Hypothyroidism in pregnancy has been shown to increase the risk of miscarriage, placental abruption, and lower IQ scores in children. Subclinical and autoimmune hypothyroidism is associated with unfavorable effects during pregnancy such as pre-eclampsia, miscarriage, and pre-term births. In addition, one study indicated decreased intelligence and motor scores in children of women with subclinical hypothyroidism. A meta-analysis revealed that subclinical hypothyroidism was associated with an increased risk of unexplained subfertility. Although the exact mechanism is unknown, studies have revealed thyroid hormone disorders disturb the development of ovarian eggs, sperm, and the fertilization process.
What are the clinical recommendations?
Recommendations to treat subclinical hypothyroidism and autoimmune disease in preconception care occur when the TSH is over 2.5 or when clinical signs coincide with basal body temperature below 97°F. Many physicians, including well-known nutrition expert Dr. Alan Gaby MD, use a desiccated thyroid hormone called Armour Thyroid, a natural preparation from porcine thyroid glands. The current conventional treatment uses Levothyroxine, a synthetic form a T4. Either way, Dr. David Berger, MD, author of From Preconception to Infancy: Environmental and Nutritional Strategies for Lowering the Risk of Autism, states that,
“Women with true hypothyroidism and those with positive antibodies (especially those with consistently low basal body temperatures under 97°F) should receive consideration for thyroid hormone supplementation and be closely monitored during both pregnancy and lactation.”
However, it is also important to address the many nutritional modifications, specifically iodine, iron, selenium, and zinc that contribute to optimal thyroid health. It is ideal to work with an experienced physician who can address the multiple facets of thyroid health before and during pregnancy.
Written by Haylee Nye, NCNM Naturopathic Medicine Program Edited by Dr Elise Schroeder
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