No abstract

Sex hormones are associated with the physiology and pathophysiology of almost all organs in the body, as well as most diseases. Interest in the associations between sex hormones and ocular tissues has increased in recent years. Androgens may have a positive effect on dry eye, whereas the effects of oestrogen on ocular conditions remain unclear. Intracrinology, the local synthesis and metabolism of hormones that is unique to humans, is of relevance to the eye and may help to explain why studies of the relationship between oestrogens and dry eye signs and symptoms are inconclusive. Knowledge of the pathways of hormone formation and metabolism is crucial to understanding the pathogenesis of ocular disease including dry eye. This review examines the mechanisms of steroidal sex hormone biosynthesis and reviews the significance of locally produced sex hormones, with a focus on ocular surface tissues. Much of the current literature is based on animal studies, which may not be transferable to humans due to the absence of intracrine production in animals. A large proportion of the human studies investigate systemic hormone levels rather than local levels. There is subsequently a need for additional studies to provide a better understanding of the local production of sex hormones within the human eye and ocular surface and to clarify the relationships between ocular levels of sex hormones and conditions including dry eye.

Abstract Accurate measurement of very low circulating estradiol (E2) (<5 pg/ml) in post-menopausal women and in mice is essential to investigating sex steroid action in target tissues. However, direct immunoassays are too inaccurate and conventional mass spectrometry-based measurement too insensitive at these serum E2 levels. We report application of an ultrasensitive method using a novel estrogen-selective derivatization in liquid chromatography-mass spectrometry to measure serum E2 with a detection limit of 0.25 pg/ml in small (0.2 ml) serum volumes that can quantify serum E2 in 98% and serum E1 in 100% of healthy post-menopausal women. Aromatase inhibitor (AI) treatment of postmenopausal women with breast cancer further reduces serum E2 by 85% and serum estrone (E1) by 80%. The wide scatter of circulating E2 in AI-treated women suggests that the degree of sustained E2 depletion, now quantifiable, may be an efficacy or safety biomarker of adjuvant AI treatment. This ultrasensitive method can also measure serum E2 in most (65%) female but not in any male mice. Further studies are warranted using this and comparable ultrasensitive LC-MS estrogen measurements to investigate the relationship of circulating E2 (and E1) in male, post-menopausal female and childhood health where accurate quantification of serum estrogens was not previously feasible. This will focus on direct impact of estrogens as well as indirect effects of androgen aromatization on reproductive, bone and brain tissues and notably the efficacy and safety of aromatase inhibitors in adjuvant breast cancer treatment.