Do abnormal thyroid stimulating hormone level values result in treatment changes? A study of patients on thyroxine in one general practice.

BACKGROUND: Hypothyroidism is a common disorder, easily treated with thyroxine therapy. Thyroid stimulating hormone level assay can detect under- or overtreatment. AIM: A study was carried out in one general practice to discover the number of people on thyroxine therapy, their care, and whether abnormal thyroid stimulating hormone level values resulted in alterations to their thyroxine dose.
METHOD: The study was undertaken in a north Suffolk general practice of 7640 patients. A computer search identified patients receiving repeat prescriptions for thyroxine therapy and their notes were studied. A thyroid stimulating hormone level value in the range of 0.3-3.8 mU l-1 was considered to indicate an appropriate thyroxine dose.
RESULTS: Thyroxine was being taken by 162 patients (2%), of whom 146 were women. Thyroid stimulating hormone level had been checked within the last year for 127 patients (78%). At their last thyroid stimulating hormone level test, 48 patients (30%) had a value above the normal range, only 21 of whom (44%) had their thyroxine dose increased as a result. The thyroid stimulating hormone level was below 0.3 mU l-1 at the last check in 38 patients (23%), only four of whom (11%) had their thyroxine dose reduced as a result.
CONCLUSION: There is often failure to adjust thyroxine dose despite abnormal thyroid stimulating hormone levels. However, more research is needed to determine the ideal thyroid stimulating hormone levels which should be aimed for in these patients, and whether tight control of thyroxine dosage is able to reduce morbidity and mortality among patients with hypothyroidism.