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-standing hypothyroidism has recently been reported using thallium-201 (201Tl) myocardial single photon emission tomography (SPET). The aim of the present study was to evaluate whether patients with short-term hypothyroidism (serum thyrotropin [TSH] levels above 30 mU/L) have an increased risk of silent myocardial ischemia. We studied 20 patients with differentiated thyroid carcinoma that had undergone thyroidectomy and ablative (131)I therapy. None of the patients had a known history of atherosclerotic cardiovascular disease. In the course of a planned follow-up examination, suppressive levothyroxine (LT4) therapy was discontinued 7 weeks prior to scintigraphy and replaced by triiodothyronine (T3) therapy for 4 weeks. No thyroid hormone medication 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 time of the examination. 20lTl-SPET was performed immediately after bicycle exercise stress test and again after a delay of 4 hours. In case of abnormal results, (n = 3) the examination was repeated after patients were euthyroid. Two patients showed effects of soft-tissue attenuation (breast attenuation in a female and diaphragmatic attenuation in a male subject). Myocardial ischemia was revealed in 1 patient but was seen in both hypothyroid and euthyroid examinations. The results of the present study show that short-term severe hypothyroidism as encountered in athyreotic patients after cessation of thyroxine medication for several weeks, is not associated with an impairment of myocardial perfusion.
Prasch
F
F
Department of Nuclear Medicine, Municipal Hospital Lainz, Vienna, Austria. prf@nuk.khl.mag.wien.gv.at
Wogritsch
S
S
Hurtl
I
I
Holm
C
C
Najemnik
C
C
Dudczak
R
R
D000328:Adult; D000368:Aged; D005080:Exercise Test; D005260:Female; D006801:Humans; D007037:Hypothyroidism / Q000150:complications* / Q000000981:diagnostic imaging / Q000188:drug therapy; D007457:Iodine Radioisotopes / Q000627:therapeutic use; D008297:Male; D008875:Middle Aged; D017202:Myocardial Ischemia / Q000000981:diagnostic imaging* / Q000209:etiology*; D013794:Thallium Radioisotopes; D013964:Thyroid Neoplasms / Q000532:radiotherapy / Q000601:surgery; D013965:Thyroidectomy; D013972:Thyrotropin / Q000097:blood; D013974:Thyroxine / Q000627:therapeutic use; D015899:Tomography, Emission-Computed, Single-Photon; D014284:Triiodothyronine / Q000627:therapeutic use
D007457:Iodine Radioisotopes; D013794:Thallium Radioisotopes; D014284:Triiodothyronine; D013972:Thyrotropin; D013974:Thyroxine