To Establish Whether Individuals With Premenstrual Dysphoric Disorder (PMDD) Demonstrate a Different Luteal-phase Sex Hormone Profile and Ratio Compared With Asymptomatic Controls.

Inclusion criteria

• Aged 18-45 years old (adults but less than the typical perimenopausal age so there is not added bias/variable)
• Regular menstrual cycles (21-35 days for the last 3 months)
• Willing and able to complete a questionnaire (no new clinical diagnosis given)
• Use home urine LH test strips to detect ovulation
• Attend a single in person on site in Lancaster mid luteal blood test sample appointment (approx 7 days post LH surge)
• Provide written informed consent
• Have sufficient English language skills to understand the patient information
• Be either in Group 1 or group 2 Group 1 (PMDD group ie case group) - self reported prior diagnosis of PMDD made by a healthcare professional (GP, psychiatrist, gynaecologist) Group 2 (Control group ie comparison group) - no prior diagnosis of PMDD made by a healthcare professional and no history of clinically significant premenstrual mood symptoms on screening

Exclusion criteria

• Current use or use in the last 3 months of hormonal contraception such as the combined oral contraceptive pill, the progestogen only pill, the implant, the injection, hormonal coil (Mirena, Kyleena) or patch/ring.
• Current use or use in the last 3 months of any hormone replacement therapy (e.g. combined oestrogen and progesterone, oestrogen and Mirena coil combination, oestrogen alone if had a hysterectomy, or progesterone alone) or GnRH analogues use
• On a selective serotonin reuptake inhibitor (SSRI) with a recent initiation or dose change within the last 3 months
• Pregnant, breastfeeding or within 3 months post partum
• Irregular menstrual cycles (outside the 21-35 day window)
• Surgical menopause
• Premature ovarian insufficiency
• Other endocrine disorders e.g. uncontrolled thyroid disease, high prolactin, cushing's syndrome, polycystic ovarian syndrome)
• Regular systemic steroid use or use of other medications known to affect sex hormone within the last 3 months
• Severe mental health issues that impair consent or participation
• Needle phobic so that venepuncture is intolerable
• The use of the emergency contraceptive pill either 3 months prior to the study or during the study.