In the absence of definitive guidelines, some clinicians may elect to perform routine screening with serum TSH measurement or to measure TSH in patients with persistent non-specific complaints, especially women, the elderly and persons with risk factors for thyroid failure Measurement of serum TSH is generally considered the best screening test for thyroid disease; increased values usually indicate hypothyroidism, and decreased values usually indicate hyperthyroidism.
In patients with coronary artery disease and minimal elevations of TSH, however, it may be advisable to follow the TSH level rather than subject the patient to the small risk of levothyroxine therapy.
In patients with subclinical hypothyroidism, not surprisingly, the same changes are present but are less marked and less consistent.
This pattern of lipid abnormalities, of course, is important because it is a risk factor for atherosclerotic cardiovascular disease.
Treatment is commonly initiated with 25 to 50 μg daily and raised by increments of 25 to 50 μg, according to TSH measurements at six- to eight-week intervals.
In patients who are elderly or debilitated, or who have heart disease, lower starting dosages and slower increases are advisable.The elevation of TSH levels reflects the sensitivity of the hypothalamic-pituitary axis to small decreases in circulating thyroid hormone; as the thyroid gland fails, the TSH level may rise above the upper limit of normal when the free T level of 6 or 7 μg per d L (77 to 90 nmol per L), although not outside the normal range of 4.5 to 12.5 μg per d L (58 to 160 nmol per L), may represent a significant fall from an original level of 9 or 10 μg per d L (116 to 129 nmol per L) and, thus, is low for this particular patient..