Endocrine Testing in Transgender Adults

Transgender individuals are those who do not identify with the sex they were assigned at birth. Some, but not all, transgender individuals seek gender-affirming interventions to help align physical characteristics with their gender identity. Hormone therapy is one such intervention, and laboratory testing plays an important role in establishing a safe and effective hormone regimen. Other medical care for transgender individuals, including preventive care screening, should be personalized based on each individual’s biology and preferences.

This ARUP Consult topic summarizes currently established recommendations, with the understanding that this field of medicine continues to evolve. Due to the paucity of data to direct treatment management for youth and adolescents, this topic focuses on laboratory testing and healthcare for transgender adults. The following resources provide more detailed recommendations, including recommendations for youth and adolescents:

For definitions of terms as they are used in this topic, refer to the Glossary section.

Quick Answers for Clinicians

Which laboratory tests are used to monitor gender-affirming hormone therapy?

Testosterone concentrations, in the case of transgender males, and testosterone and estradiol concentrations, in the case of transgender females, should be measured regularly during and after gender-affirming hormone therapy.   Testing by tandem mass spectrometry is more specific and accurate than immunoassay across a wider range of hormone concentrations; this method is preferable if low concentrations of a specific hormone are expected (eg, at baseline or at initiation of some gender-affirming hormone therapies). Testing by immunoassay is accurate at higher hormone concentrations and may be more cost-effective when clinically appropriate (eg, for monitoring long-term gender-affirming hormone therapy use).

See the Monitoring of Gender-Affirming Hormone Therapy testing algorithm for a visual representation. Laboratory tests should also be used to evaluate other secondary health risks of hormone therapy, such as metabolic and electrolyte imbalances. 

Which reference intervals should be used for hormone testing in transgender individuals?

The typical goals of gender-affirming hormone therapy are to suppress endogenous sex steroids and maintain exogenous sex steroids within the reference interval of the affirmed gender or within a range that achieves the desired outcome.   Broadly applicable and well-studied reference intervals specific for transgender patients have not been established. In many cases, the applicable reference intervals for the affirmed gender may provide an initial goal, but results should be interpreted with caution and in the context of the clinical situation. The Endocrine Society Clinical Practice Guideline  and UCSF Transgender Care and Treatment Guidelines  provide more specific guidance.

Where can I find more information about ARUP estrogen and testosterone test options?

For comparisons of ARUP estrogen and testosterone tests, refer to the Estrogen Tests Comparison and Testosterone Tests Comparison tables.

Which testing algorithms are related to this topic?

Treatment Monitoring

Youth and Adolescents

For recommendations for adolescents, refer to the Endocrine Society Clinical Practice Guideline.  The UCSF Transgender Care and Treatment Guidelines  and WPATH Standards of Care  also offer guidance for children and adolescents.

Adult Transgender Males on Testosterone Hormone Therapy

Monitoring of Hormone Therapy

The Endocrine Society Clinical Practice Guideline  recommends that serum testosterone concentrations be measured every 3 months until serum testosterone is within the reference interval for an adult cisgender male. The UCSF Transgender Care and Treatment Guidelines  suggest that annual monitoring is reasonable after reaching the desired range. Timing of measurements depends on the type of therapy used.

  • For testosterone enanthate/cypionate injections, the suggested serum testosterone concentration is 400-700 ng/dL; measurements can be taken either midway between injections or at peak and trough concentrations. 
  • For parenteral testosterone undecanoate, the dose interval should be increased if testosterone concentrations are <400 ng/dL. Measurements should be taken right before the next injection (ie, at trough concentrations). 
  • For transdermal testosterone, measurements should be taken no sooner than after 1 week of daily application and at least 2 hours after application. 

Testing can be performed using either tandem mass spectrometry or immunoassay. Tandem mass spectrometry is more specific and accurate across a wider range of concentrations and is preferable if low testosterone concentrations are expected (eg, at baseline or at initiation of some gender-affirming hormone therapies). Testing by immunoassay is accurate at higher hormone concentrations and may be more cost-effective when clinically appropriate (eg, for monitoring long-term gender-affirming hormone therapy use).

Free or bioavailable testosterone tests may provide supportive information for patients with unexpected responses to hormone therapy.  Free and bioavailable testosterone concentrations are typically estimated using calculations that include testosterone, albumin, and/or sex hormone-binding globulin (SHBG) measurements.  Tests that measure SHBG may be useful in individuals with protein-binding abnormalities. Equilibrium dialysis may be used for the direct measurement of free testosterone, but it is not frequently used as a first-line test for monitoring of hormone therapy. Calculated methods of determining free testosterone concentrations are sufficient in most clinical circumstances.

For a visual overview of testing associated with this topic, please refer to the Monitoring of Gender-Affirming Hormone Therapy testing algorithm.

For a comparison of ARUP testosterone tests, refer to the Testosterone Tests Comparison table.

Other Testing

In addition to serum testosterone measurements, the Endocrine Society Clinical Practice Guideline  recommends the following tests or assessments. Additional tests may also be recommended by other organizations.

  • Clinical assessment of masculinization and monitoring for adverse reactions should be performed every 3 months in the first year, then once or twice yearly. 
  • Hematocrit or hemoglobin should be tested before beginning gender-affirming hormone therapy, then every 3 months during the first year of therapy, and then once or twice yearly. 

Adult Transgender Females on Estrogen Hormone Therapy and/or Testosterone-Suppressing Hormone Therapy

Monitoring of Hormone Therapy

The Endocrine Society Clinical Practice Guideline  recommends that serum testosterone and serum estradiol concentrations be measured every 3 months. These and other guidelines suggest a goal of testosterone concentrations <50 ng/dL and serum estradiol concentrations within the peak physiologic range of 100-200 pg/mL.  The UCSF Transgender Care and Treatment Guidelines  recommend measurement of estradiol at 3 months, 6 months, and then as needed, and recommend total testosterone and SHBG/albumin (to calculate bioavailable testosterone) at 3 months, 6 months, and 1 year.

Testing can be performed using either tandem mass spectrometry or immunoassay. Tandem mass spectrometry is more specific and accurate across a wider range of concentrations and is preferable if low hormone concentrations are expected (eg, at baseline or at initiation of some gender-affirming hormone therapies). Testing by immunoassay is accurate at higher hormone concentrations and may be more cost-effective when clinically appropriate (eg, for monitoring long-term gender-affirming hormone therapy use). Equilibrium dialysis may be used to directly measure free estradiol in individuals on hormonal contraception and/or with protein-binding abnormalities.

Free or bioavailable testosterone tests may provide supportive information for patients with unexpected responses to hormone therapy.  Free and bioavailable testosterone concentrations are typically estimated using calculations that include testosterone, albumin, and/or SHBG measurements.  Tests that measure SHBG may be useful in individuals who have protein-binding abnormalities or are taking estrogen supplementation.

For a visual overview of testing associated with this topic, please refer to the Monitoring of Gender-Affirming Hormone Therapy testing algorithm.

For comparisons of ARUP estrogen and testosterone tests, refer to the Estrogen Tests Comparison and Testosterone Tests Comparison tables.

Other Testing

In addition to serum hormone measurements, the Endocrine Society Clinical Practice Guideline  recommends the following tests or assessments. Additional tests may also be recommended by other organizations.

  • Clinical assessment of feminization and monitoring for adverse reactions should be performed every 3 months in the first year, then once or twice yearly. 
  • Serum electrolyte concentrations (particularly potassium concentrations) should be measured every 3 months, then annually in individuals on spironolactone.  The UCSF Transgender Care and Treatment Guidelines  also recommend the assessment of renal function.
  • Prolactin concentrations should be monitored periodically in transgender individuals treated with estrogens. 

Preventive Care Screening

The following preventive screenings for applicable health risks are recommended as part of treatment monitoring. Other screenings may also be recommended.

  • Osteoporosis screening should be performed in individuals who stop testosterone treatment or otherwise develop risk for bone loss. 
  • Routine cancer screening should be performed for all tissues present.  For example, cervical cancer screening, if cervical tissue is present, should be performed according to the recommendations from the American College of Obstetricians and Gynecologists.   Breast cancer screenings for individuals who retain breast tissue should follow recommendations for cisgender women.  Alternative breast cancer screening strategies may be needed for individuals who have had a mastectomy.  Screening should be performed according to individual risk for prostatic disease and prostate cancer. 
  • Cardiovascular disease risk should be assessed in transgender individuals treated with hormones. 

Glossary

This glossary is presented solely to define terms as they are used in this ARUP Consult topic and the following resources:

This glossary is intended to facilitate appropriate laboratory test selection for individuals who are on gender-affirming hormone therapy. The terminology in this field changes rapidly, and these terms may be used differently by others and in different contexts.

Sex and Gender Terms

Cisgender female: An individual with a female gender identity who was assigned a female sex at birth.

Cisgender male: An individual with a male gender identity who was assigned a male sex at birth.

Gender: Nonbiologic characteristics (eg, behaviors, roles, social attributes) that a culture associates with an individual’s sex.  Gender identity is defined as an individual’s internal sense of their gender.   

Gender dysphoria: Distress associated with discordance between an individual’s gender identity and their sex assigned at birth.   

Sex: A combination of biologic characteristics (eg, chromosomes, genes, genitalia, gonads, hormones, secondary sex characteristics). Sex is often assigned at birth based on external genital anatomy.    

Transgender female: An individual with a female gender identity who was assigned a male sex at birth.   

Transgender male: An individual with a male gender identity who was assigned a female sex at birth.   

Hormone Therapy Terms

Estrogen hormone therapy: Hormone treatment intended to maintain exogenous estrogen within a desired range.

Estrogen-suppressing hormone therapy: Hormone treatment intended to suppress an individual’s endogenous estrogen to within a desired range. This may include aromatase inhibitor therapies.

Gender-affirming hormone therapy: Hormone treatment that is intended to help change an individual’s physical characteristics to best align with their gender identity. This may include therapies to suppress endogenous sex steroids and/or maintain exogenous sex steroids within a desired physiologic range.

Testosterone hormone therapy: Hormone treatment intended to maintain exogenous testosterone within a desired range.

Testosterone-suppressing hormone therapy: Hormone treatment intended to suppress an individual’s endogenous testosterone (or testosterone activity) to within a desired range. This may include antiandrogen therapies such as spironolactone and cyproterone.

ARUP Laboratory Tests

Testosterone

For a comparison of ARUP testosterone tests, refer to the Testosterone Tests Comparison table.

Individuals on Testosterone Hormone Therapy

Use this immunoassay to monitor testosterone hormone therapies

Free or bioavailable testosterone measurements may provide supportive information

This test is not recommended when low testosterone concentrations, such as those found in children and cisgender females, are expected

Provides a calculated value for free testosterone concentration using total testosterone measured by immunoassay

May be used to monitor testosterone hormone therapies

This test is not recommended when low testosterone concentrations, such as those found in children and cisgender females, are expected

Provides a calculated value for free testosterone concentration using total testosterone measured by immunoassay

May be used to monitor testosterone hormone therapies

This test is not recommended when low testosterone concentrations, such as those found in children and cisgender females, are expected

Provides a calculated value for bioavailable testosterone concentration using total testosterone measured by immunoassay

May be used to monitor testosterone hormone therapies

This test is not recommended when low testosterone concentrations, such as those found in children and cisgender females, are expected

Laboratory reference method for the direct measurement of free testosterone

These tests are not recommended when low testosterone concentrations, such as those found in children and cisgender females, are expected

Individuals on Testosterone-Suppressing Hormone Therapy

Use this mass spectrometry test to measure a wide range of testosterone concentrations

Most useful when low concentrations are expected, regardless of the patient’s sex assigned at birth

Use to monitor testosterone-suppressing hormone therapies (eg, antiandrogens or estrogens)

Free or bioavailable testosterone measurements may provide supportive information 

Provides a calculated value for free testosterone concentration using total testosterone measured by mass spectrometry

May be used monitor testosterone-suppressing hormone therapies (eg, antiandrogens or estrogens)

Provides a calculated value for free testosterone concentration using total testosterone measured by mass spectrometry

May be used to monitor testosterone-suppressing hormone therapies (eg, antiandrogens or estrogens)

Provides a calculated value for bioavailable testosterone concentration using total testosterone measured by mass spectrometry

May be used to monitor testosterone-suppressing hormone therapies (eg, antiandrogens or estrogens)

Estrogens

For a comparison of ARUP estrogen tests, refer to the Estrogen Tests Comparison table.

Individuals on Estrogen Hormone Therapy

Use this immunoassay to measure estradiol in individuals on estrogen hormone therapies

This test is not recommended when low estradiol concentrations, such as those found in children, cisgender males, and postmenopausal females, are expected

Individuals on Estrogen-Suppressing Hormone Therapy

Use this mass spectrometry test to measure a wide range of estradiol concentrations

Most useful when low estradiol concentrations are expected, regardless of the patient’s sex assigned at birth

Use to monitor estradiol in individuals on estrogen-suppressing hormone therapies (eg, aromatase inhibitors or testosterone)

Individuals on Hormonal Contraception and/or with Protein-Binding Abnormalities

Use to directly measure free estradiol

May be used to evaluate estradiol status for individuals with protein-binding abnormalities or individuals on hormonal contraception

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