Subclinical Changes in Luteal Function in Cynomolgus Monkeys with Moderate Blood Lead Levels

The objective of the present study was to investigate luteal function in cynomolgus monkeys (n = 32), aged 15-20 years with blood lead levels (BLLs) in the range of < 3.0 micrograms dl-1 (control, n = 20), 10-15 micrograms dl-1 (low, n = 7) and 25-30 micrograms dl-1 (moderate, n = 5). Sampling was performed daily beginning with day 10 of the menstrual cycle and concluding on the first day of the subsequent menstrual cycle. Circulating levels of oestradiol (E2), progesterone (P4) and 20 alpha-hydroxyprogesterone (20-OHP) were normalized to the day of the ovulatory E2 surge. The area under the concentration curve (AUC) for P4 was significantly lower in monkeys with moderate BLLs compared to the control group (P = 0.04). The number of days for which circulating levels of P4 were greater than 1.0 ng ml-1 were also significantly fewer (P = 0.03) in monkeys with moderate BLLs compared to controls. There was no statistical evidence of a lead effect on circulating levels of E2, 20-OHP or menstrual cycle characteristics. These data suggest that chronic lead exposure suppresses corpora luteal production of P4 in the monkey at circulating BLLs lower than previously reported and relevant to humans with occupational exposure to lead.