Discordance Between Growth Hormone (GH) Responses After GH-Releasing Hormone and Insulin Hypoglycemia in Myotonic Dystrophy

Plasma GH responses to human GHRH, arginine, l-dopa, and insulin-induced hypoglycemia were determined in seven myotonic dystrophy (MD) patients. An iv bolus injection of GHRH-(1-44)-NH2 (1 μg/kg BW) only slightly increased plasma GH concentrations in MD patients. The mean peak plasma GH level after GHRH injection [4.2 ± 0.8 (±se) μg/L] was significantly lower than that in 10 age-matched normal subjects (26.7 ± 4.3 μg/L) or that in 6 patients with progressive muscular dystrophy (22.8 ± 6.6 μg/h) whose nutritional status was similar to that of the MD patients. Even with a larger dose of GHRH (3 /g/kg BW), the plasma GH rises were minimal in the MD patients (mean peak, 5.9 ± 1.8 μg/L). The plasma GH responses to a 30-min iv infusion of arginine (0.5 g/kg BW) and oral ingestion of l-dopa (0.5 g) were attenuated to a similar extent, whereas insulin-induced hypoglycemia caused a significant increase in plasma GH in all seven MD patients [mean peak, 17.4 ± 4.1 (±se) μg/L]. The plasma TSH responses to TRH and pla...