We have previously described severe hyperparathyroidism during the pubertal growth spurt in three uremic adolescents treated with recombinant human growth hormone (rhGH). Here we investigate the possible role of puberty in the genesis of hyperparathyroidism during rhGH treatment of a large cohort of patients. Data from 67 uremic patients treated with rhGH from five Italian pediatric nephrology centers were retrospectively recorded every 3 months starting 1 year before rhGH administration. The mean (+/-SD) rhGH treatment observation period was 19.9+/-5.9 months. The mean age at the start of rhGH treatment was 8.3+/-3.6 years. Of the 67 patients, 15 reached pubertal stage 2 during the 1st year of rhGH treatment and 12 of these 15 progressed to pubertal stage 3. The relative increase in parathyroid hormone (PTH) levels after rhGH initiation was greater in pubertal [1.95, 95% confidence interval (CI) 1.43-2.66] than in prepubertal patients (1.19, 95% CI 1.01-1.40). Increases in PTH levels were significantly different between the two groups (Delta=1.64, 95% CI 1.16-3.19, P=0.007). Multiple regression analysis showed an inverse correlation between PTH and calcium levels and a positive correlation between PTH and pubertal stage 3. There was no correlation with phosphate levels and calcitriol dosage. In conclusion, these results suggest that in uremic adolescents treated with rhGH puberty may influence PTH levels.