In this issue of the Journal of Endocrinology, we are taking the relatively rare step of publishing an article under a ‘Hypothesis’ banner. Publication of novel endocrine hypotheses has been an underexploited option in this journal for some years. This may simply relate to the fact that many scientists formulate a hypothesis and then proceed to test it in experiments reported in a research paper. In James (2008) which will be published in this issue however, Dr James, a self-confessed non-endocrinologist with extensive experience in epidemiology presents his ideas on the influence of the sex hormones on the ratio of male to female conceptions and births. He would agree that the endocrinology underlying this hypothesis is untested and speculative, but he believes that only by subjecting these ideas to an endocrine audience will they be fully considered and the hypothesis tested. Dr James' approach is an epidemiological one and hence this offers no mechanistic explanation for his observations. He, and the editors, hope that this will stimulate novel research initiatives which may ultimately lead to greater understanding of the biology of conception.
James WH 2008 Evidence that mammalian sex ratios at birth are partially controlled by parental hormone levels around the time of conception. Journal of Endocrinology 198 3–14.