To clarify the pathogenesis of growth retardation in patients with Ullrich-Turner's syndrome (TS) we have investigated basal SmC/IGF-I, insulin and prolactin concentrations. Compared with 56 age matched healthy controls basal SmC/IGF-I concentration in 51 patients with TS older than 9-11 years was significantly lower (age group 13-14 years; TS 273 +/- 47 and controls 479 +/- 114 ng/ml). Mean basal prolactin level in 43 patients with TS (406 +/- 211 microU/ml) was significantly higher (p less than 0.01) than in 192 female controls (age 3-11 years; 264 +/- 176 microU/ml). Basal insulin concentration in 28 TS patients in comparison to 20 healthy children of a control group was significant higher (TS 18 +/- 8 microU/ml; controls 9 +/- 4 microU/ml; p less than 0.01). It seems that neither insulin nor prolactin are relevant stimulators of Smc/IGF-I in man, especially in patients with gonadal dysgenesis. Considering these results we speculate that despite higher prolactin and higher insulin levels in TS, the lower SmC/IGF-I concentrations may be predominantly related to the abnormal sex steroid secretion.