SUMMARY Nine children with Duchenne muscular dystrophy were given Sanorex (mazindol), a growth hormone inhibitor, daily for 6 months. There was no significant change in their muscle function, but there was a significant reduction in weight gain and in levels of growth hormone, somatomedin C, hair zinc, serum zinc, and serum LDH. Selenium and glutathione peroxidase in the serum increased significantly. Thirteen other children with growth hormone deficiency had a significant reduction in hair selenium following growth hormone administration.These results show a significant relationship between growth hormone and selenium nutritional status and confirm our previous reports indicating an effect of growth hormone on zinc nutritional status. It is possible that prolonged therapy with a growth hormone inhibitor would attenuate the course and improve the longevity of patients with muscular dystrophy.In a recent report of a family with Duchenne muscular dystrophy, an affected brother with growth hormone deficiency was substantially less disabled than his younger sibs.' Based on this observation, we decided to evaluate the effect of administering a growth hormone inhibitor to nine children with Duchenne muscular dystrophy. MethodsThe nine children studied had been followed for 1 to 9 years in our Muscular Dystrophy Clinic. Their diagnosis had been confirmed by the typical clinical course, characteristic physical findings, which included pelvifemoral weakness and calf pseudohypertrophy, family history, raised serum levels of creatinine kinase (CK), lactate dehydrogenase (LDH), and serum glutamate oxaloacetate transaminase (SGOT), and abnormal findings on muscle biopsy and electromyography. The ages of these nine children at the time of entry into the study were 5, 6, 7, 7, 8, 10, 12, 12, and 14 years.After a group discussion with all the parents, and individual discussions, a written informed consent *Supported in part by a grant from the Muscular Dystrophy Association, Nassau Chapter. Received for publication 21 October 1983. Accepted for publication 17 November 1983. was obtained for each child. The study was approved by our institutional research committee (IRB).Each child received Sanorex 8 (mazindol) at a dose of 2 mg daily for 6 months. Careful manual muscle testing and peak flow during forced expiration were done for each child at the beginning of the study and at 3 and 6 months by one of us (JK), and accurate measurements of height and weight were done by at least two of us at each examination. Laboratory tests were also performed at the beginning of the study and at 3 and 6 months. Human growth hormone was assayed in serum obtained before and 90 minutes after the oral administration of clonidine (0 1 to 0 2 mg). Selenium was assayed in serum and hair by the fluorometric method.2 Glutathione peroxidase, CK, LDH, and SGOT were assayed by standard methods. Hair and serum zinc were assayed by atomic absorption spectrophotometry. Somatomedin C was assayed by radioimmunoassay. Parents were instructed in the method o...