1. Sulphobromophthalein (BSP) retention and liver glutathione levels were studied in uncomplicated hyperthyroid patients.
2. BSP retention was increased in 52.5% of the subjects at admission (n = 40) and in 28% of the cases after 3 months of propylthiouracil treatment (300–400 mg/day) (n = 25).
3. Hepatic levels of glutathione were measured in six patients and significant inversed power correlation with BSP retention was observed (r = 0.968, P < 0.001).
4. These data support the contention that the alteration of the BSP retention observed in hyperthyroidism could be due to a decreased availability of hepatic glutathione for conjugation.