Increased need for thyroxine in women with hypothyroidism during estrogen therapy

Article Abstract:

Women with hypothyroidism who begin taking estrogen replacement therapy should have their thyroid hormones checked about 12 weeks later. Estrogen affects the concentration of thyroid hormones, so these women may need higher doses of thyroxine.

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Estrogen, thyroxine binding in serum, and thyroxine therapy

Article Abstract:

Women who are taking thyroid hormone may need to take a higher dose if they begin taking estrogen replacement therapy. This is necessary because estrogen increases the amount of thyroxine-binding globulin, a protein that normally binds to thyroid hormone.

Editorial

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Therapy of hypothyroidism: when are changes needed?

Article Abstract:

Treatment options for people with hypothyroidism (inadequate production of thyroid hormone, which is important in many metabolic processes) are reviewed and evaluated. An article in the July 12, 1990 issue of The New England Journal of Medicine concluded that pregnant women with primary hypothyroidism needed more thyroid hormone (thyroxine) than they had been taking prior to pregnancy. In general, when blood levels of thyroid hormone fall, levels of thyrotropin (the hormone that stimulates its production) increase dramatically. Thyrotropin is made by cells in the pituitary gland that sense circulating levels of thyroid hormone and are very sensitive to small changes in hormone concentrations. Thus, measurement of thyrotropin levels is a good indicator of the efficacy of thyroxine therapy. Minor aberrations from the normal concentration are no cause for concern, except in cases such as pregnancy, where fetal and maternal health could be affected. Although the thyroid gland normally secretes both thyroxine and triiodothyronine, the only substance needed by hypothyroid people is thyroxine, since much of the triiodothyronine is made from thyroxine in non-thyroid tissues. Administration of extra quantities of this substance can throw off the body's physiological balance. Most hypothyroid adults need 100 micrograms of thyroxine daily, a lower dose than formerly recommended. Ideal doses can be calculated using new tests that allow very sensitive monitoring of thyrotropin levels. Patients who take thyroxine are often noncompliant, taking more when they feel they need it, or stopping treatment if all goes well. Dosage alteration may be required because of ongoing disease processes, or the administration of different hormones or drugs for treating other conditions. Age and body weight can affect the way thyroxine is cleared from the body; older adults need less than younger adults. Dose levels need careful consideration in patients with ischemic heart disease (where the blood supply to the heart is insufficient) or thyroid cancer. However, appropriate treatment of hypothyroidism is usually not difficult. (Consumer Summary produced by Reliance Medical Information, Inc.)

Evaluation, Drug therapy, Dosage and administration, Thyroxine, Endocrine gland diseases, Endocrine diseases, editorial

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