Evaluation of Luteal-phase Sex Hormone Profile and Ratio in Premenstrual Dysphoric Disorder (PMDD)

Premenstrual dysphoric disorder (PMDD) is a severe cyclical disorder characterised by affective, cognitive and physical symptoms occurring during the luteal phase of the menstrual cycle and resolving shortly after the onset of menstruation. Although circulating ovarian hormone concentrations are generally considered to be within physiological reference ranges, increasing evidence suggests that altered sensitivity to normal hormonal fluctuations, rather than absolute hormone concentrations alone, may contribute to symptom development. The progesterone-to-oestradiol ratio has been proposed as a potential biological marker of luteal hormonal balance; however, this has not been systematically evaluated in individuals with PMDD compared with asymptomatic controls. This observational case-control study will compare serum progesterone concentrations, serum oestradiol concentrations, and the progesterone-to-oestradiol ratio during the mid-luteal phase between participants with PMDD and healthy controls. Hormone measurements will be obtained following confirmation of ovulation using a urinary luteinising hormone (LH) surge, with blood sampling performed approximately seven days after the LH surge to standardise assessment within the mid-luteal phase. The findings will provide preliminary evidence regarding whether alterations in the progesterone-to-oestradiol ratio are associated with PMDD and may inform future mechanistic studies investigating the endocrine basis of the disorder.