A single 6-g dose of aluminum hydroxide was given to eight patients on regular hemodialysis before and 3 days after parathyroidectomy (PTX). Serum aluminum levels were measured before and after 5 h after ingestion of aluminum hydroxide to examine indirectly the effects on absorption of aluminum from the gastrointestinal tract of both high and low parathyroid hormone (PTH). Plasma PTH levels fell significantly from 2,724 +/- 1,830 ng/l (mean +/- SD) before PTX to 352 +/- 63 ng/l after PTX. However, no significant change was detected in serum aluminum levels before or after PTX (1.45 +/- 0.96 to 1.92 +/- 0.88-mu-mol/l before PTX; 2.02 +/- 1.41 to 2.89 +/- 1.19 mol/l after). These findings indicate that in patients with chronic renal failure, high plasma levels of PTH are not associated with significant increases in serum aluminum concentrations after ingestion of a large quantity of aluminum hydroxide. Parathyroid hormone may not enhance intestinal absorption of aluminum in humans.