Elderly Persons.[ref. 10]--In many cases, hypothyroidism in elderly patients is characterized by a paucity of specific signs and symptoms. The symptoms may be subtle and include hoarseness, deafness, confusion, dementia, ataxia, depression, dry skin, or hair loss. Because of high prevalence of hypothyroidism in women past 60 years of age, it is recommended that such individuals be screened with a serum TSH measurement. All patients with a prior history of any medically or surgically treated thyroid disease should be screened with a serum TSH measurement yearly. In addition, patients with other autoimmune diseases and those with unexplained depression, cognitive dysfunction, or hypercholesterolemia should be screened with TSH measurements. Therapy should be directed at using the dose of levothyroxine required to maintain normal TSH concentrations.

Pregnancy.[ref. 11]--During pregnancy, many hypothyroid patients have an increase in levothyroxine requirement, which can be detected with a TSH measurement. The patient should be checked during each trimester to make sure that the TSH concentration is still normal, with further adjustments as indicated by the appropriate testing. The levothyroxine dose should return to the prepregnancy dose immediately after delivery and a serum TSH level should be obtained 6 to 8 weeks post partum.

Iatrogenic Hyperthyroidism.[ref. 9][ref. 12]--Some patients, especially elderly patients, tolerate the effects of excess T[sub]4[/sub] poorly. If symptoms of palpitations, tremor, difficulty in concentrating, or chest pain develop, the patient should be evaluated with appropriate tests, and if hyperthyroidism is confirmed, the current dose of levothyroxine should be withheld for 1 week and restarted at a lower dose. Other patients remain asymptomatic despite elevations of free T[sub]4[/sub] and/or suppression of TSH concentrations. Since levothyroxine overreplacement has been associated with reduced bone mineral content, particularly in postmenopausal women, it is recommended that these patients have their dose reduced until the TSH concentration is normalized, unless TSH suppression is the objective, as in patients with a history of well-differentiated thyroid cancer.

Subclinical Hypothyroidism.[ref. 9, 10]--As many as 15% of patients older than 65 years, as well as many other adults, have a normal free T[sub]4[/sub] estimate (or normal direct free T[sub]4[/sub] measurement) and an elevated TSH concentration, but few, if any, hypothyroid symptoms. This state is referred to as "subclinical hypothyroidism." Some patients with this mild disorder feel better when treated with levothyroxine. Therapy for subclinical hypothyroidism is probably advisable, especially if thyroid autoantibodies are positive, because overt hypothyroidism develops with high frequency in such patients. If the physician decides not to treat these patients, they should be evaluated at yearly intervals for evidence of more severe clinical and biochemical loss of thyroid function.

Myxedema Coma.[ref. 8]--Coma caused by myxedema is a rare, life-threatening state in which severe, usually long-standing hypothyroidism markedly worsens. In general, it occurs in elderly individuals and is usually precipitated by an intercurrent medical illness. The clinical manifestations, in addition to obtundation or coma, may include hypothermia, bradycardia, respiratory failure, and even cardiovascular collapse.

Therapy of myxedema coma includes intravenous administration of levothyroxine and/or liothyronine sodium as well as pharmacologic doses of glucocorticoids. Also, precipitating or associated disorders must be aggressively treated.

Patients with myxedema coma should be treated in the intensive care unit with appropriate monitoring and with the participation of an endocrinologist.