Severe short-term hypothyroidism is not associated with an increased incidence of myocardial ischemia as assessed by thallium-201 stress/rest myocardial scintigraphy

Reversible silent myocardial ischemia associated with treatment of long-sta nding hypothyroidism has recently been reported using thallium-201 (Tl-201) myocardial single photon emission tomography (SPET). The aim of the presen t study was to evaluate whether patients with short-term hypothyroidism (se rum thyrotropin [TSH] levels above 30 mU/L) have an increased risk of silen t myocardial ischemia. We studied 20 patients with differentiated thyroid c arcinoma that had undergone thyroidectomy and ablative I-131 therapy. None of the patients had a known history of atherosclerotic cardiovascular disea se. In the course of a planned follow-up examination, suppressive levothyro xine (LT4) therapy was discontinued 7 weeks prior to scintigraphy and repla ced by triiodothyronine (T-3) therapy for 4 weeks. No thyroid hormone medic ation was given during the 3 weeks preceding the diagnostic procedures. All patients were hypothyroid (TSH 87.2 +/- 30.8 mU/L, mean +/- SD) at the tim e of the examination. Tl-201-SPET was performed immediately after bicycle e xercise stress test and again after a delay of 4 hours. In case of abnormal results, (n = 3) the examination was repeated after patients were euthyroi d. Two patients showed effects of soft-tissue attenuation (breast attenuati on in a female and diaphragmatic attenuation in a male subject). Myocardial ischemia was revealed in 1 patient but was seen in both hypothyroid and eu thyroid examinations. The results of the present study show that short-term severe hypothyroidism as encountered in athyreotic patients after cessatio n of thyroxine medication for several weeks, is not associated with an impa irment of myocardial perfusion.