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Bone
Gómez Acotto et al., Buenos Aires, Argentina, and Lyon, France, measured bone mass, using ultrasound assessment of the calcaneus and body composition, and bone mineral density by DEXA in 24 untreated hyperthyroid women. Both, ultrasound results and DEXA bone mineral density values, were similarly decreased in hyperthyroid patients. Lean tissue and fat mass were also decreased as measured by DEXA. The authors conclude that in this study the ultrasound technique is the first application for measuring bone mass in patients with hyperthyroidism, showing its potential for future application. Brucker-Davis et al., Bethesda, MD, measured bone density in 9 females and 8 males with resistance to thyroid hormone (RTH). In this familial syndrome sensitiviy to thyroid hormone is decreased because of a mutation in the gene of the á receptor of thyroid hormone. It is known that in hypothyroidism, when it occurs in childhood, stature may be short and this occurs also in about 20% of patients with RTH. In the here reported study bone mineral density was measured of the lumbar spine, femur and radius. Seven subjects had bone mineral density below 2 SD and 8 below 1 SD. Spine and femur were equally affected and more often than the radius. Both genders were equally affected and a correlation was found between the percentile of the height and bone mineral density at the level of the spin. Heart Biondi et al., Naples, Italy, performed Doppler echocardiography in 83 patients with variable degree of hyper- and hypothyroidism. They found left ventricular mass to be increased in overt hypothyroidism and longterm subclinical hyperthyroidism. Heart rate was increased in subclinical- and overt hyperthroidism, and reduced in overt hypothyroidism. Systolic function was increased in both types of hyperthyroidism. Aortic acceleration (change in the acceleration of aortic blood flow with stress testing) was increased in subclinical- and clinical hyperthyroidism and decreased in hypothyroidism. Both, circumferential fiber shortening and aortic acceleration, showed a significant direct correlation with FT3 and FT4, and those indices are thus very useful as a biological index of thyroid hormone. Shapiro et al., New York, NY, duplicated studies by Biondi et al. from Italy (JCEM 77: 334, 1993 and 80: 2222, 1995) where they tested the effect of suppressive doses of T4 on heart performence. The dose of T4 was titrated to just suppress serum TSH to 0.01 mU/mL. In the Italian study various effects were found: increased values of: basal heart rate, incidence of atrial extrasystoles, interventricular septal thickness, and left ventricular mass index, while diastolic heart function was impaired. In the present study, performed in 17 athyreotic patients who were treated with suppressive T4 with a mean duration of 8.0 years, only an increased left ventricular mass index was found. The authors conclude that, as an increased left ventricular mass index without impaired heart function seems to have no clinical consequences, that T4 may be prescribed in suppressive doses without clinical consequence. (Comment: The gross discrepancies between this study and the Italian studies are not easy to explain. The mean T4 dose per kg bodyweight in the New York study was quite similar to that in the Italian studies.) Mohr-Kahaly et al., Mainz, Germany, performed dynamic stress echocardiography and cardiopulmonary exercise testing in 42 patients with hyperthyroidism before treatment and also after 3 months of euthyroidism. The most important finding was an impaired chronotropic response during exercise in hyperthyroidism, and the authors conclude that this might be the primary limiting factor of reduced work capacity that is present in untreated hyperthyroidism. |
