We studied catch-up growth following withdrawal of glucocorticoid administration in seven intact prepubertal cynomolgus monkeys. To reduce stress during blood sampling, a vascular access port was implanted subcutaneously in each animal for the duration of the study. After a baseline observation period of 50 weeks, the monkeys received injections of dexamethasone at a dose of 100 micrograms.kg-1.day-1 for 15 weeks. Growth velocity was monitored every 3 weeks by measuring lower leg length and body weight. Spontaneous serum growth hormone (GH) concentrations and GH levels after insulin and L-dopa stimulation, as well as serum insulin-like growth factor I (IGF-I) and plasma thyrotropin, triiodothyronine and thyroxine, were measured during the study. Differences between animals were analyzed by repeated measures analysis of variance and Student's paired t-test. Mean +/- SEM growth velocity (mm/3 weeks) decreased from 0.90 +/- 0.08 during the baseline period to 0.29 +/- 0.07 (p < 0.001) during the period of growth retardation, and increased to 1.23 +/- 0.2 (p < 0.001) during the period of catch-up growth. Spontaneous GH and peak GH levels following insulin did not show any significant variation during the study. Peak GH during the L-dopa test decreased from 15.4 +/- 3.2 micrograms/l during the baseline period to 6.2 +/- 2.4 micrograms/l during the period of growth retardation (p < 0.05), and increased to 23.0 +/- 5.9 micrograms/l during the period of catch-up growth (p < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)