Reproductive Endocrinology Reference Intervals for Transgender Women on Stable Hormone Therapy

Area of Science:

• Reproductive endocrinology
• Transgender health
• Hormone therapy monitoring

Background:

• Feminizing hormone therapy, often involving estrogen, alters the reproductive hormone axis in transgender women and nonbinary individuals.
• Current reference intervals for reproductive hormones do not account for the unique physiological state of transgender women on feminizing therapy.
• Establishing specific reference intervals is essential for appropriate clinical management and monitoring of gender-affirming care.

Purpose of the Study:

• To derive and establish reference intervals for commonly measured reproductive endocrine analytes in transgender women undergoing feminizing hormone therapy.
• To provide a basis for accurate interpretation of hormone levels in this population.
• To inform clinical practice for transgender healthcare providers.

Main Methods:

• Recruited 93 healthy transgender individuals on feminizing hormone therapy for at least one year.
• Measured total testosterone, estradiol, LH, FSH, SHBG, prolactin, progesterone, AMH, and DHEAS using immunoassay and mass spectrometry.
• Calculated reference intervals (central 95%) following Clinical Laboratory Standards Institute guidelines.

Main Results:

• Hormone level distributions in transgender women differed significantly from cisgender reference ranges.
• Spironolactone use was associated with altered results for AMH, FSH, LH, and progesterone.
• Immunoassay was adequate for most estradiol and total testosterone measurements; free testosterone offered limited additional clinical value over total testosterone.

Conclusions:

• Specific reference intervals for reproductive endocrine analytes in transgender women are necessary for accurate assessment.
• Spironolactone is an important variable to consider when interpreting hormone test results in transgender women.
• These findings support the need for updated clinical guidelines in transgender healthcare.