Forty-two women with idiopathic infertility of 1 to 12 years' duration were treated empirically with desiccated thyroid. The initial dose was 1 grain per day; for patients who did not respond, the dose was gradually increased, as tolerated. Twenty-eight similar patients received a placebo. Ten women (23.8%) became pregnanct after 1 to 12 months of thyroid therapy, compared with 10.7% of those receiving placebo. Although this difference was not statistically significant, the response rate was more than double in the active-treatment group than in the placebo group.
Comment: Hypothyroidism is a known reversible cause of infertility. Most doctors rely on laboratory tests to diagnose hypothyroidism, but there is a considerable amount of anecdotal evidence that standard thyroid-function tests fail to detect a large proportion of cases of clinical hypothyroidism (Gaby AR. "Sub-laboratory" hypothyroidism and the empirical use of Armour thyroid. Altern Med Rev 2004;9:157-179.). I have seen many women with signs and symptoms suggestive of hypothyroidism (e.g., fatigue, depression, cold extremities, dry skin, constipation, thinning hair, menstrual irregularities, delayed Achilles tendon reflexes) who were treated with thyroid hormone empirically despite having normal laboratory tests. It was not uncommon to see pregnancies rapidly ensue in women who previously had been unable to conceive. Thyroid hormone should not be used indiscriminately, but a therapeutic trial for infertile women with clinical evidence of hypothyroidism is not unreasonable.
Thyroid treatment should not be discontinued during pregnancy, as doing so may increase the risk of a miscarriage. If anything, thyroid hormone requirements increase during pregnancy. On the other hand, the use of excessive doses of thyroid hormone during pregnancy may also increase the risk of miscarriage (JAMA 2004;292:691-5), so clinical status should be monitored carefully.
Buxton CL, Herrmann WL. Effect of thyroid therapy on menstrual disorders and sterility. JAMA 1954;155:1035-1039.
