Patulin is a mycotoxin produced by several species of Penicillium, Aspergillus and Byssachlamys. Patulin can be produced on different food products including fruits, grains, cheese, cured meats, but in natural situations patulin is usually found in apple and apple products. In the present study, the time-dependent effects of patulin on the T-3, T-4, thyroid stimulating hormone, testosterone, luteinizing hormone and growth hormone levels of growing male rats were investigated. Patulin, at a dose of 0.1 mg/kg bw/day, was administered by gavage to growing male rats aged 5-6 weeks for a period of 60 or 90 days. The dose of patulin used in the present study was based on estimated human exposure levels. At the end of the experiment, serum T-3, T-4, TSH, testosterone, LH and GH levels of rats in control and treatment groups were analysed. In addition, the thyroid and testes were histopathologically examined by light microscopy. Results revealed that while patulin caused an increase (66.6%) in testosterone levels and a decrease (17.3%) in T-4 levels of rats treated for 60 days, there was no change in the other hormone levels compared to those of the control group. When patulin treatment was extended to 90 days, increased serum testosterone (75%) and LH levels (146%) were observed. In histological examinations of the testes of rats treated with patulin, oedema, fibrosis and local Leydig cell hyperplasia in the interstitial tissue, and disorganization of seminiferous tubule epithelium were also observed. In addition, the thyroid of rats treated with patulin revealed lymphoid cell inflitration and enlargement of interstitial tissue between follicles, and degenerated colloid. (C) 2004 Elsevier Ltd. All rights reserved.