Growth hormone deficiency in patients with histiocytosis X

Twenty-two patients with biopsy proved histiocytosis X, aged 10 months to 14 years (median 2 years) at the time of diagnosis, were observed for 6 months to 13 years (median 4 years). One patient who had received 3000 rads irradiation directly to the hypothalamic-pituitary area had clinical and biochemical evidence of growth hormone deficiency and responded to GH therapy. Thirteen patients had normal stature, normal growth velocity, and no diabetes insipidus. The GH response to insulin-induced hypoglycemia was studied in three of these 13 patients (group 1), in three children with short stature and no diabetes insipidus (group 2), and in five patients with diabetes insipidus but normal stature and growth velocity (group 3). Peak GH responses were normal (greater than 5 micrograms/L) in all patients in groups 1 and 2, but three of the five patients in group 3 had subnormal GH responses to insulin-induced hypoglycemia and to arginine, L-DOPA/propranolol, and exercise. Their growth rates continue to be normal over 6 to 14 years follow-up. Thus, although impaired GH responses were observed in four of the 12 patients tested, true growth failure occurred only in association with direct hypothalamic-pituitary irradiation. This experience and the observation that GH deficiency was diagnosed in fewer than 1% of children with histiocytosis in Canada during a 15-year period (accounting for less than 1% of all children with GH deficiency) suggest that classic GH deficiency is not a common complication of histiocytosis unless direct hypothalamic-pituitary irradiation has been given.