Abstract
Hexachlorobenzene (HCB) is a known reproductive toxin. However, the full spectrum of its reproductive toxicity is unknown. Consequently, the effect of HCB on serum oestradiol (E~2~) and progesterone (P~4~) concentrations during the follicular (days 1β9), periovulatory (days 10β14) and luteal (days 15 to beginning of next menses) phases was investigated in the spontaneously cycling cynomolgus monkey. Adult female cynomolgus monkeys (n = 16) were randomly assigned to one of four treatment groups and orally dosed with gelatin capsules containing HCB (0.0, 0.1, 1.0 and 10.0 mg kg^β1^ body wt. day^β1^) mixed with glucose. A 10βweek acclimitization phase was followed by 13 weeks of dosing. HCB induced a doseβdependent suppression of serum P~4~ concentrations during the luteal phase. However, circulating levels of P~4~ were unaffected during the follicular and periovulatory phases of the menstrual cycle. Serum E~2~ concentrations, body weight, menstrual cycle length and duration of menses were not affected by HCB treatment. The range of menstrual cycle length and duration range of menses, however, were broader in the highest dose group. We conclude that HCB interfers with mechanisms regulating ovarian steroidogenesis and suppresses P~4~ levels during the luteal phase in the cynomolgus monkey.