[Intracellular signal transduction of endocrine organs and expanded DNA fragment size in myotonic dystrophy].

The Ellsworth-Howard (EH) test was performed in 16 patients with myotonic dystrophy (DM), who were divided into two groups according to serum calcium level; Group I showing normal serum calcium (8 patients) and Group II with hypocalcemia (8 patients). Patients in Group II were recognized as having pseudohypoparathyroidism (PHP) type II and those in Group I as normal. Therefore, it was suggested that an abnormality of A kinase might be present in Group II patients. We additionally performed the thyrotropin releasing hormone (TRH) tolerance test in the same patients and 7 normal controls to examine an abnormality of C kinase. delta TSH (delta TSH: peak minus pre TSH) values in DM patients were significantly lower than those in normal controls. Moreover, delta TSH values in Group II were significantly lower than those in Group I. It was suggested that the abnormality of C kinase might be present in Group II patients. Taken together, our results indicated that some patients with DM might possess abnormalities of signal transduction of both A and C kinases. We compared the degree of endocrine involvement determined by both the EH test and the TRH tolerance test with expanded DNA fragment (EF) size determined by standard Southern blot analysis using an appropriate cDNA probe (cDNA25 probe). There was significant negative correlation between EF size and the results of the EH test and negative correlation between the EF size and the results of the TRH tolerance test. These findings suggested that EF size might be correlated with disease severity in affected endocrine organs.