This study will find out what the reference intervals are for common blood tests in transgender people taking hormone therapy.

Reference intervals help doctors interpret blood test results. They are expressed as two numbers, and most normal results fall between them. If a results fall outside of them, it may be because of a disease. Some blood tests are also affected by normal difference between people, such as age, sex or ethnicity. For these tests, different reference intervals are given for each group of people. Having accurate reference intervals benefits patients because it allows doctors to identify disease faster.

Transgender people have a gender identity which does not match their sex characteristics at birth. Gender identity is the feeling of being a gender, and sex is the biological aspects of growing up male or female. Transgender people may use hormone therapy to help change their appearance to fit their gender identity. This involves taking either oestrogen or testosterone.

For blood tests which are affected by sex, it is not clear what reference intervals should be used for transgender people who are on hormone therapy. This is because they have a mixture of male and female sex characteristics. Answering this question will allow doctors to identify disease in them faster.

The study will take place at cliniQ, at King's College Hospital, which provides health services to transgender people. It will recruit healthy transgender people who attend the clinic for blood tests to monitor their hormone therapy. Participants will fill out a questionnaire, give a urine sample, then have their appointment as normal. Extra tests will also be performed on their blood sample. The aim is to recruit 240 participants. Participant's tests results will then be used to calculate reference intervals.

The study is funded by Viapath Group LLP.

Inclusion Criteria:

• Transgender or nonbinary people.
• Aged 18 or older.
• Taking testosterone or oestrogen therapy.
• For 12 months or more.
• Having routine hormone therapy monitoring at the clinic.

Exclusion Criteria:

• Unable to give informed consent (including participants who cannot communicate in English).
• History of chronic liver disease, chronic kidney disease, diabetes, or severe cardiovascular disease (including myocardial infection, deep vein thrombosis, stroke and pulmonary embolism).
• Blood test results that indicate severe disease.
• Pregnant or within one year after childbirth.
• Other conditions which could put participants at risk by participating, or which could influence the results of the study.

Patients are eligible if they are transgender, that is, their gender is different from their sex assigned at birth.

Healthy transgender adults who have been taking masculinising for feminising hormone therapy for at least 12 months.

The full protocol, deidentified participant-level data and the analysis files will be uploaded to an open access repository within 6 months of the publication of the findings.

Within 6 months of the publication of the results of the research.

Public access to deidentified data.