Adequate restitution in primary hypothyroidism depending on levothyroxine formulations

The prevalence of primary hypothyroidism (PH) is around 3.8%-4.6% in general population. Out of patients under treatment with levothyroxine, approximately 40% show altered levels of thyroid-stimulating hormone (TSH).

To determine the prevalence of euthyroid sick syndrome in patients under treatment for PH in two local clinics, considering that the number of formulations of levothyroxine could be a contributing factor to the inadequate restitution.

Descriptive, comparative cohort conducted with PH patients who were treated with a stable dose of levothyroxine for at least six months. Patients treated with mixtures of liothyronine/levothyroxine, with postsurgical hypothyroidism, pregnant, breastfeeding or mentally ill were discarded. Medical clinic 1 was a public center that had only access to levothyroxine of 100 µg, and medical clinic 2 was a private clinic with access to 25, 50, 75 and 100 µg levothyroxine formulations.

A total of 350 patients were evaluated. 190 patients were obtained at clinic 1, and 160 patients at clinic 2. At clinic 1, only 63% received the appropriate dose, while at clinic 2, 75% were medicated with the correct dose (p = 0.033).

In the public center, 39% of patients did not receive appropriate dose of levothyroxine; however, in the private clinic, which had more drug formulations, the percentage of patients lowered to 25%. Therefore, the number of formulations could be a factor for the risk of inadequate restitution.