A history of gastric bypass surgery alone is not considered a risk factor for poor absorption of thyroid hormone, given that the majority of levothyroxine absorption occurs in the ileum.19,20 However, advancing age (> 70 years) and extreme obesity (BMI > 40) are independent risk factors for decreased levothyroxine absorption.20,21
Women of reproductive age and pregnant women. Overt untreated or undertreated hypothyroidism can be associated with increased risk of maternal and fetal complications including decreased fertility, miscarriage, preterm delivery, lower birth rates, and infant cognitive deficits.3,22 Therefore, the main focus should be optimization of thyroid hormone levels prior to and during pregnancy.3,4,8,22 Thyroid hormone replacement needs to be increased during pregnancy in approximately 50% to 85% of women using thyroid replacement prior to pregnancy, but the dose requirements vary based on the underlying etiology of thyroid dysfunction.
One initial option for patients on a stable dose before pregnancy is to increase their daily dose by a half tablet (1.5 × daily dose) immediately after home confirmation of pregnancy, until finer dose adjustments (usually increases of 25%-60% ) can be made by a physician. Experts recommend that a TSH level be obtained every 4 weeks until mid-gestation and then at least once around 30 weeks’ gestation to ensure specific targets are being met with dose adjustments.22 Optimal thyrotropin reference ranges during conception and pregnancy can be found in the literature.23
Patients who have positive antibodies and normal thyroid function tests. Patients who are screened for thyroid disorders may demonstrate normal thyroid function (ie, euthyroid) with TSH, free T4, and, if checked, free T3, all within normal ranges. Despite these normal lab results, patients may have additional test results that demonstrate positive thyroid autoantibodies including thyroglobulin antibodies and/or thyroid peroxidase antibodies. Thyroid autoimmunity itself has been associated with a range of other autoimmune conditions as well as an increased risk of thyroid cancer in those with Hashimoto thyroiditis.24 Two studies showed that prophylactic treatment of euthyroid patients with levothyroxine led to a reduction in antibody levels and a lower TSH level.25,26 However, no studies have focused on patient-oriented outcomes such as hospitalizations, quality of life, or symptoms. If the patient remains asymptomatic, we recommend no treatment, but that the patient’s TSH levels be monitored every 12 months.27
Elderly patients. Population data have shown that TSH increases normally with age, with a TSH level of 7.5 mIU/L being the upper limit of normal for a population of healthy adults > 80 years of age.28,29 Overall, studies have failed to show any benefit in treating elderly patients with subclinical hypothyroidism unless their TSH level exceeds 10 mIU/L.6,21 The one exception is elderly patients with heart failure in whom untreated subclinical hypothyroidism has been shown to be associated with higher mortality.30
Continue to: Elderly patients are at higher risk...