Iatrogenic Hyperthyroidism in a Community Hospital

Despite the availability of progressive refinements in TSH testing that allow refinements in appropriate dosing of thyroid hormone, even studies performed within the last five years report that more than one-third of patients treated for hypothyroidism demonstrate excessive suppression of TSH (TSH levels > 0.1 micro-units/mL). Since excess thyroid hormone is a risk factor for osteoporosis and cardiac disease, the authors studied the prevalence of excessive TSH suppression with thyroid hormone in a large community hospital.

Of 1652 prescriptions for levothyroxine in a one-year period, 905 were accompanied by TSH testing. In this group of patients, 12.2% had suppression of TSH to less than 0.1 microunits/mL. Although some of the over-suppressed patients had indications like thyroid cancer and nodular thyroid disease, more than half had no such indication and, hence, were considered subject to the potential deleterious consequences of excess thyroid hormone. Women were almost three times as likely to be oversuppressed as men, which, of course, is of special concern, particularly among postmenopausal women. It is suggested that clinicians apprise patients of the necessity for limiting thyroid replacement to the therapeutic range.

Watsky JG, Koeniger MA. J Am Board Fam Pract 1998;11:175-179.