Abnormal Calcium Metabolism in Myotonic Dystrophy
Increased Level of Serum 1, 25 (OH) 2 D Concentration and Augmented Intestinal Calcium Absorption
1986 Volume 62 Issue 10 Pages 1203-1211
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1986 Volume 62 Issue 10 Pages 1203-1211
Myotonic dystrophy (MyD) is a multisystemic disorder characterized by muscle weakness, myotonia, cataract and frontal baldness. Several endocrinological abnormalities are also known in this disorder. Although presence of bone changes, such as hyperostosis, has been frequently reported in MyD patients, there have been few published papers in which calcium metabolism was precisely examined. The present study was designed to elucidate the possibility of the presence of abnormal calcium metabolism in MyD by using the oral calcium tolerance test.
Ten patients with MyD, 11 patients with other neuromuscular disorders (non-MyD) and 9 healthy control subjects were investigated according to the method of Broadus et al. Increments of serum and urinary calcium levels after oral calcium load (1 gram) were determined as indices of intestinal calcium absorption.
There were no significant differences in basal plasma calcium and phosphate levels among the three groups. Plasma 1, 25 (OH) 2D level in MyD (38.0 ± 11.8pg/ml, Mean ± SD) was significantly higher than those in the other two groups (normal subjects 21.8 ± 7.0; P<0.01, non-MyD 21.8 ± 12.0; P<0.01), respectively. In contrast, plasma 25 (OH) D and 24, 25 (OH) 2D levels were not significantly different among these groups. Fasting urinary calcium excretion in both MyD (0.151 ± 0.069mg/100mlGF) and non-MyD (0.141 ± 0.077) was significantly higher than that in normal subjects (0.064 ± 0.048). Calcemic response in MyD (1.08 ± 0.20mg/dl) was significantly increased when compared with that in normal subjects (0.72 ± 0.34, P<0.02) and non-MyD (0.54 ± 0.31, P<0.001). Calciuric response in MyD (0.245 ± 0.110mg/100mlGF) was also higher than that in normal subjects (0.126 ± 0.075, P<0.02) and in non-MyD (0.108 ± 0.074, P<0.01). There were significant correlations between plasma 1, 25 (OH) 2 D levels and calcemic responses, and plasma 1, 25 (OH) 2 D levels and calciuric responses (P<0.02, P<0.05).
The present study shows that intestinal calcium absorption was increased in MyD patients, probably due to the elevation of plasma 1, 25 (OH) 2D level.
