Short stature is one of the major symptoms in Turner's syndrome (TS). The cause of short stature is not clearly known at present. In this study we initially assessed GH secretory status in TS by determinations of urinary human (h) GH excretion for 2 consecutive days. Secondly, the therapeutic dose of hGH used for treatment of short stature in TS was evaluated by measurements of urinary hGH after recombinant hGH (r-hGH) injections. Twenty-four-hour urinary hGH excretion for the 2 days combined was significantly lower in patients with TS than in normal children [2.3 +/- 1.8 ng/day (n = 7) vs. 13.4 +/- 3.2 (n = 16); P less than 0.001], although four of seven patients with TS had normal GH responses to the provocative tests. The mean level of urinary hGH in TS after 2 days was comparable to that in complete GH deficiency (1.9 +/- 0.9 ng/day; n = 14) that we previously reported. Treatment with daily sc injections of 1.0 IU (0.37 mg)/kg.week r-hGH, given in seven divided doses, normalized urinary hGH excretion and induced remarkable catch-up growth in all patients with TS. These results indicate that the 24-h endogenous GH secretion in seven patients with TS is impaired. The measurement of 24-h urinary hGH excretion may prove to be useful as a marker to assess the abnormal GH secretion and the adequacy of treatment with hGH in patients with TS. The therapeutic dose of hGH in TS is approximately 0.37 mg/kg.week, given in seven divided doses. To convert international units of r-hGH to milligrams, divide by 2.7.