Diagnosis Recommendations for screening for thyroid disorders in women range from every 5 years starting at age 35 in women (American Thyroid Association), to age 50 (American College of Physicians), to periodically in older women (American Academy of Family Physicians and American Association of Clinical Endocrinologist), to evidence is insufficient to recommend for or against screening (United States Preventive Services Task Force) (45–49).
Suspected hypothyroidism should always be confirmed with laboratory studies. Primary hypothyroidism is characterized by the combination of an elevated serum TSH with a low serum free T4 level. Autoimmune thyroiditis can be confirmed by the presence of serum antithyroid peroxidase (formerly referred to as antimicrosomal) antibodies. An elevated TSH with a normal free T4 level implies subclinical hypothyroidism. Central hypothyroidism, although rare, is distinguished by a low or low-normal serum free T4 level with either a low or inappropriate normal serum TSH concentration.
Therapy Synthetic L-thyroxine (T4) is the treatment of choice for hypothyroidism and is available as generic levothyroxine. There is debate about the value of replacing thyroxine in the subclinical hypothyroidism patient. Such replacement did not result in improved survival, decreased cardiovascular morbidity, or improve quality of life (44). The mode of action is by conversion of T4 to T3 in peripheral tissues. Levothyroxine should be taken on an empty stomach. Absorption may be poor when taken in combination with aluminum hydroxide (common in antacids), cholestyramine, ferrous sulfate, or fatty meals. The usual T4 requirement is weight related (approximately 1.6 μg/kg) but decreases for the elderly. Normal daily dosage is 0.1 to 0.15 mg but should be adjusted to maintain TSH levels within the normal range. TSH levels should be checked in 6 weeks and when dosages or brands are changed.
In the early 1980s, many clinicians thought that increasing the serum T4 to mildly elevated levels would enhance conversion of T4 to T3. Subsequent data proved that even a mild increase of T4 was associated with cortical bone loss and atrial fibrillation, particularly in older women (44). A low initial T4 dose (0.025 mg per day) should be initiated in the elderly or patients with known or suspected coronary artery disease. Rapid replacement may worsen angina and in some cases induce myocardial infarction.
Hyperthyroidism Hyperthyroidism affects 2% of women during their lifetime, most often during their childbearing years and impacts women fivefold more commonly than men. Graves disease represents the most common disorder; it is associated with orbital inﬂammation, causing the classic exophthalmus associated with the disease and a characteristic dermopathy, pretibial myxedema. It is an autoimmune disorder caused by TSH reception antibodies that stimulate gland growth and hormone synthesis. The etiology of Graves disease in genetically susceptible women is unknown. Autonomously functioning benign thyroid neoplasias are less common causes of hyperthyroidism and are associated with toxic adenomas and toxic multinodular goiter. Transient thyrotoxicosis may be the result of unregulated glandular release of thyroid hormone in postpartum (painless, silent, or lymphocytic) thyroiditis and subacute (painful) thyroiditis. Other rare causes of thyroid overactivity include human chorionic gonadotropin–secreting choriocarcinoma, TSH-secreting pituitary adenoma, and struma ovarii. Factitious ingestion or iatrogenic overprescribing should be considered in patients with eating disorders.