Endocrine aspects of cancer: an epidemiological approach.

Over the last 2 decades epidemiologists have increasingly used parameters of endocrine function in their studies. Prospective cohort studies offer methodological advantages in view of the latency between the relevant hormonal exposure and the clinical onset of cancer. Examples from the author's experience are provided. Evidence is mounted for an important "time window" for breast cancer development between menarche and the birth of a first child.