Hormone Testing for Male Hypogonadism
Order a morning total testosterone level (drawn between 8-10 AM) on two separate occasions as the initial diagnostic test, followed by luteinizing hormone (LH) and follicle-stimulating hormone (FSH) if testosterone is confirmed low. 1
Initial Diagnostic Testing
Primary hormone to order:
- Morning total testosterone measured between 8 AM and 10 AM on at least two separate days 1, 2, 3
- Diagnosis requires both measurements to be below 300 ng/dL 1
- Use the same laboratory and same assay method for consistency 1
Additional baseline hormones if testosterone is borderline (near 300 ng/dL):
- Free testosterone by equilibrium dialysis in men with obesity or suspected SHBG abnormalities 2, 4
- Sex hormone-binding globulin (SHBG) to calculate free testosterone index, particularly important in men with liver disease or obesity 1, 2
Adjunctive Hormone Testing After Confirming Low Testosterone
Once low testosterone is confirmed (<300 ng/dL on two occasions), the following hormones are mandatory:
To Determine Etiology (Primary vs Secondary Hypogonadism):
- Luteinizing hormone (LH) - Strong recommendation, Grade A evidence 1
- Follicle-stimulating hormone (FSH) - Strong recommendation, Grade A evidence 1
If LH/FSH Are Low or Low-Normal:
- Serum prolactin - Strong recommendation, Grade A evidence 1
If Fertility Is a Concern:
- FSH (if not already measured) to assess spermatogenesis 1
- Consider semen analysis if FSH is elevated (hypergonadotropic hypogonadism) 1
If Breast Symptoms or Gynecomastia Present:
- Serum estradiol prior to starting testosterone therapy 1
- Refer to endocrinology if estradiol is elevated at baseline 1
Critical Diagnostic Algorithm
Step 1: Morning total testosterone × 2 (separate days, 8-10 AM) 1, 2
Step 2 (if both <300 ng/dL): LH + FSH 1
Step 3 (if LH/FSH low or low-normal): Prolactin 1
Step 4 (if testosterone <150 ng/dL with low/low-normal LH): Pituitary MRI regardless of prolactin level 1
Step 5 (if fertility desired): FSH + semen analysis 1
Common Pitfalls to Avoid
- Never diagnose hypogonadism based on a single testosterone measurement - diurnal variation and assay variability require confirmation 1
- Never order testosterone at random times of day - must be morning (8-10 AM) samples 1, 2
- Never skip LH/FSH testing - distinguishing primary from secondary hypogonadism is critical for treatment selection, especially regarding fertility preservation 1, 2
- Never start testosterone therapy without measuring prolactin in men with low/low-normal LH - you may miss a prolactinoma 1
- Never use screening questionnaires as a substitute for laboratory testosterone measurement - they lack specificity and sensitivity 1
Additional Pre-Treatment Laboratory Tests
Before initiating testosterone therapy, also measure: