The ages and TSH values of patients being prescribed levothyroxine

Levothyroxine is a commonly prescribed medication. Some data suggest that levothyroxine may be initiated for mild degrees of hypothyroidism and used without considering age-specific reference ranges or individual patient factors when prescribing.

The electronic medical record of a health care system operating in the Washington, DC and Maryland area was interrogated to determine the number of patients who were being prescribed levothyroxine during the time period 2008-2016, the number of prescriptions supplied to these individuals, an associated diagnosis of hypothyroidism, and whether the prescriptions were new or existing prescriptions. Information was also extracted about the age of patients receiving prescriptions and the thyroid stimulating hormone level documented prior to levothyroxine initiation.

Although the number of levothyroxine prescriptions provided annually increased over this time period, when corrected for the number of patients in the database, the percentage of patients receiving levothyroxine prescriptions showed a slight downward trend. Levothyroxine was both most frequently prescribed and frequently initiated in those of ages 50-59 years and 60-69 years. The doses of levothyroxine most commonly prescribed were 50 µg and 100 µg and the pattern of levothyroxine doses being used was unaffected by whether a diagnosis of hypothyroidism was documented or not. Levothyroxine prescription initiation was associated with mean thyroid stimulating hormone values that were modestly elevated and in the range of 7.5-13.8 mIU/L.

This analysis showed that although the percentage of patients being prescribed levothyroxine is stable or slightly declining, with most decrement in those without a diagnosis of hypothyroidism, there is nevertheless continued initiation of levothyroxine in those with mild degrees of thyroid stimulating hormone elevation, and in those of older age, raising concerns about both unnecessary treatment and iatrogenic thyrotoxicosis. Such data suggest the need for great consideration of both the degree of thyroid stimulating hormone elevation and the patient context when considering whether treatment of an elevated thyroid stimulating hormone value, versus ongoing monitoring, is indicated.