Subnormal 24-hour mean concentration and abnormal 24-hour profile of plasma LH in the luteal phase in women with breast cancer

24-hour mean plasma LH content was measured during the follicular phase of the menstrual cycle in 7 women with breast cancer (all stages), rigorously selected to exclude factors known or suspected to alter endocrine function, and in 9 healthy control women. Similar studies were done in the luteal phase in 7 cancer patients (all stages) and in 5 normal controls. In addition, LH concentrations were measured every 20 minutes for 24 hours in 5 of the 7 luteal-phase cancer patients and in 1 of the luteal-phase controls (24-hour plasma LH profile). In the follicular phase, 5 of the 7 cancer patients had 24-hour mean LH levels within the normal range, while 2 patients had markedly subnormal levels (4.4 and 7.4 standard deviations below the normal mean). In the luteal phase, all 7 cancer patients had 24-hour mean LH levels at or below the lowest value in normal controls; the mean of the cancer group was 6.3 mIU/ml, compared with a mean of 18 mIU/ml in the controls (p<0.005). The 24-hour plasma LH profiles were abnormal in all 5 of the luteal-phase cancer patients studied, in that both the frequency and amplitude of episodic secretory pulses were markedly subnormal. This is believed to represent a human counterpart of the slow-GnRH-pulsing model described in primates. Recent observations in this laboratory show a similar LH abnormality in healthy obese premenopausal women, and it seems possible that this abnormality may represent the first plausible mediator of the increased breast cancer risk that is seen in obesity.