What do the investigators know already? Many women suffer loss of periods (amenorrhoea). One of the most common causes of period loss is called 'functional hypothalamic amenorrhea' (FHA). FHA is difficult to diagnose and may be mistaken for other conditions causing period loss, such as polycystic ovarian syndrome (PCOS). This could cause delays in starting the correct treatment.

What is the justification for doing this study? Undiagnosed women with FHA are predisposed to complications related to low oestrogen levels, such as osteoporosis, bone fractures and infertility. The failure to accurately identify women with FHA and mislabel those women with FHA as having PCOS, may delay appropriate treatment. Treatment delay causes harm for affected women, including bone fractures and infertility.

What do the investigators propose? Improve the diagnosis of women with FHA by composing an assessment score, which could be used by women to improve the accuracy of diagnosing FHA. The investigators designed a questionnaire based on literature search, which can be used to identify women with FHA. A questionnaire-based study (on-line or in person) will be performed to identify risk of FHA, in women referred to hospital with period loss.

A questionnaire was developed to be used by women with period loss to facilitate the diagnosis of women with FHA. The development of the questionnaire was based on systematic literature review and comments from a small patient involvement group, as per National Institute for Health and Care Research (NIHR) INVOLVE guidelines.

Participants will be recruited via distributing a patient information sheet, consent form and a questionnaire to all women referred with amenorrhea to the Endocrinology or Reproductive Medicine clinics at Imperial College Healthcare NHS Trust and/or participating NHS organisations. Completion of the consent form and questionnaire is entirely dependent on each potential participant's choice.

Every woman taking part can complete the questionnaire before or after her appointment. All questionnaires will be anonymised with a unique study code, and handed back to the NHS clinician.

Inclusion Criteria:

• Any woman 18-58 years of age
• Secondary amenorrhea defined by either menstrual cycle interval persistently exceeding 45 days and/or those with period loss for 3 months or more

Exclusion Criteria:

• Women who never had periods (primary amenorrhea).

All women referred by their GP with amenorrhea to the Endocrinology or Reproductive Medicine clinics at Imperial College Healthcare NHS Trust hospitals and participating NHS organisations.