Baseline Laboratory Testing for Gender-Affirming Hormone Therapy
Before initiating gender-affirming hormone therapy, obtain baseline complete blood count, comprehensive metabolic panel (including liver function tests), lipid panel, hemoglobin A1c (if diabetic or family history of diabetes), and sex hormone levels (testosterone and estradiol). 1
Essential Baseline Labs
The Endocrine Society guidelines specify the following baseline laboratory evaluation prior to hormone initiation:
For All Patients (Both Transfeminine and Transmasculine):
- Complete blood count (CBC) - establishes baseline hemoglobin and hematocrit 1
- Liver function tests (ALT, AST) - critical as cross-sex hormones are hepatically metabolized 1
- Lipid panel - baseline cardiovascular risk assessment 1
- Fasting blood glucose if family history of diabetes 1
- Hemoglobin A1c if diabetic 1
- Weight and blood pressure - cardiovascular monitoring 1
Hormone-Specific Baseline Testing:
- Testosterone level - for transmasculine patients to establish baseline 1
- Estradiol level - for transfeminine patients and transmasculine patients (to confirm pubertal levels in adolescents) 1
Additional Considerations:
Bone mineral density (BMD) testing should be obtained at baseline only if specific risk factors are present, including: previous fracture, family history of osteoporosis, glucocorticoid use, or prolonged hypogonadism 1. This is not routine for all patients.
Thrombophilia screening is not recommended routinely but should be restricted to those with a personal or family history of venous thromboembolism 1. The evidence shows that routine screening of all patients is not warranted, as one Dutch study found no venous thromboembolism despite 8% incidence of thrombophilia in screened patients 1.
Prolactin levels are not required at baseline but should be monitored during treatment in transfeminine patients on estrogen 1.
Critical Pitfalls to Avoid
Do not order D-dimer monitoring - this is explicitly not recommended during treatment 1.
Do not perform universal thrombophilia screening - only screen if there is personal or family history of clotting 1.
Avoid ethinyl estradiol - synthetic estrogens like ethinyl estradiol carry significantly higher thromboembolism risk (20-fold increase reported) and cannot be monitored by serum levels 1. Use bioidentical estradiol preparations instead.
Monitoring Schedule After Initiation
Once hormone therapy begins, the guidelines recommend:
- Every 2-3 months during the first year for clinical and laboratory monitoring 1
- Then 1-2 times yearly thereafter 1
Recent evidence from adolescent populations suggests that abnormal laboratory results, if they occur, typically manifest within the first 6 months of therapy 2. Studies in adults show most analytes reach stable levels within 6 months, though some parameters (HDL, LDL, platelets) may continue changing beyond the first year 3.
Medical Conditions Requiring Pre-Treatment Evaluation
The guidelines explicitly state that medical conditions that can be exacerbated by hormone depletion and cross-sex hormone treatment must be evaluated and addressed prior to initiation 1. This includes cardiovascular disease, diabetes, liver disease, and thromboembolic risk factors. Patients with these conditions require in-depth risk-benefit discussions but are not automatically excluded from therapy 1.