Levothyroxine prescriptions trends may indicate a downtrend in prescribing

There has been a trend for increased prescribing of levothyroxine (LT4) in many countries, including the United States. Several different factors have been suggested to be the cause of this practice pattern. These factors include increased size of the United States population, more diagnosis of hypothyroidism, more treatment of minimally elevated thyroid-stimulating hormone (TSH) levels, more use of LT4 in older patients, and use of LT4 for treatment of euthyroid patients with non-thyroidal conditions.

The electronic databases of the MedStar Health system operating in the Washington, DC and Maryland areas were 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, the associated diagnosis, and whether the prescriptions were new or existing prescriptions. Regression analyses were also performed to determine the prescribing trends during this time period.

Although the annual number of levothyroxine prescriptions increased during this time period, the percentage of patients in the database receiving levothyroxine for hypothyroidism initially increased and then decreased over time (2.5% to 3.2% to 2.5%). The percentage of prescriptions written for patients who did not appear to carry a diagnosis of hypothyroidism steadily declined (3.5% to 1.0%). Although the percentage of patients with existing prescriptions for hypothyroidism initially increased and then were maintained at steady levels (1.4% to 2.4% to 2.2%), a smaller percentage of patients with existing prescriptions were documented over time when there was no diagnosis of hypothyroidism (1.45% to 0.89%). The percentage of patients with new prescriptions declined over time for all groups. The number of annual 90-day period prescriptions increased over the time for patients with a diagnosis of hypothyroidism, but down-trended starting over the latter part of the time period for those patients without a diagnosis of hypothyroidism.

Taken together, these data suggest that there may be a stabilization, and even a down-trend in levothyroxine prescribing with the MedStar system. The decrease in levothyroxine prescribing appears to be accounted for by less use of levothyroxine without an established diagnosis of hypothyroidism, and less initiation of new prescriptions.