Primary somatomedin deficiency. Case report.

A child presenting with the clinical features of hyposomatotropism but with high immunoreactive plasma growth hormone is described. During short-term administration of human growth hormone (HGH) his response with regard to fasting blood-glucose and free fatty acids, plasma-somatomedin, urinary excretion of calcium, nitrogen, and hydroxyproline was minimal or absent. 6 months of treatment with HGH did not reduce the endogenous HGH secretion. Insulin secretion had not increased and plasma somatomedin levels remained extremely low. Over a period of 2 years of treatment, growth response and loss of subcutaneous fat were minimal. On serial dilution in radioimmunoassay, his growth hormone (GH) molecule yielded a parallel line with the HGH standard. In electrofocusing experiments the GH molecule was in the same H range as growth hormone in acromegalic plasma and the major peak of clinical grade HGH (5·03 against 5·01 and 4·98). It is concluded that an overall and specific diminished responsiveness to HGH is present in this patient. This includes a lack of generation of somatomedin, which is thought to be the cause of his short stature. There was no evidence of abnormality of the GH molecule.