What does a total testosterone of 113 ng/dL, free testosterone of 21.7 pg/mL, and bioavailable testosterone of 40.3 ng/dL indicate, and what is the appropriate evaluation and treatment?

Severe Hypogonadism Requiring Evaluation and Treatment

Your testosterone levels indicate severe hypogonadism (total testosterone 113 ng/dL) that warrants immediate further evaluation and likely testosterone replacement therapy if you have symptoms.

Interpretation of Your Laboratory Values

Your total testosterone of 113 ng/dL is markedly below the diagnostic threshold for hypogonadism. The 2018 AUA guideline establishes that total testosterone below 300 ng/dL supports the diagnosis of low testosterone 1. Your level is less than half this threshold, placing you in the severely hypogonadal range. The Endocrine Society guidelines similarly use 300 ng/dL as the cutoff 2.

Your free testosterone of 21.7 pg/mL is also significantly low. Recent standardized reference intervals show the lower limit of normal for free testosterone is approximately 66 pg/mL in adult men and 120 pg/mL in men aged 19-39 years 3. Your bioavailable testosterone of 40.3 ng/dL is similarly depressed.

All three testosterone measurements confirm severe biochemical hypogonadism.

Required Next Steps for Evaluation

1. Confirm the Diagnosis with Repeat Morning Testing

You need a second early morning (before 10 AM) total testosterone measurement to confirm the diagnosis 1. The 2018 AUA guideline provides a strong recommendation (Grade A evidence) that diagnosis requires two separate morning measurements 1. This is critical because:

• 30% of men with mildly low initial values normalize on repeat testing 2
• 15% of healthy men may have transiently low values 2

However, given your severely low level (113 ng/dL), confirmation is more of a formality—values this low rarely normalize without intervention.

2. Distinguish Primary vs. Secondary Hypogonadism

Measure LH and FSH levels immediately 2. This distinction is therapeutically critical:

• High LH/FSH = Primary testicular failure: Fertility cannot be restored with hormonal therapy; options limited to donor sperm, adoption, or intracytoplasmic sperm injection 2
• Low or normal LH/FSH = Secondary (pituitary/hypothalamic) hypogonadism: Fertility can potentially be restored with appropriate hormonal stimulation 2

3. Additional Workup Based on LH/FSH Results

If secondary hypogonadism (low/normal LH and FSH):

• Measure serum prolactin 2
• Check iron saturation (hemochromatosis screening) 2
• Obtain pituitary MRI if:
  • Total testosterone <150 ng/dL (which applies to you) 2
  • Hyperprolactinemia is present
  • Symptoms of mass effect (headaches, visual changes)
  • Evidence of panhypopituitarism

If primary hypogonadism (high LH and FSH):

• Obtain karyotype to exclude Klinefelter syndrome 2

4. Assess for Reversible Causes

Before finalizing the diagnosis, exclude 2:

• Acute or subacute illness (do not diagnose during acute illness)
• Medications: opiates, high-dose glucocorticoids, chronic corticosteroids 1, 4
• Nutritional deficiencies or eating disorders
• Excessive exercise
• Chronic conditions: HIV/AIDS, chronic infections, COPD 1, 4

5. Baseline Testing Before Treatment

Obtain these baseline values 5:

• Hematocrit: Baseline >50% is a relative contraindication to testosterone therapy 5
• PSA and digital rectal exam (if age ≥40 years): Baseline PSA >0.6 ng/mL requires closer monitoring 5
• Lipid panel and glucose: Screen for metabolic syndrome and diabetes 1
• Bone mineral density (DXA scan): Recommended for severe hypogonadism or history of low-trauma fracture 2

6. Document Symptoms and Signs

The diagnosis requires BOTH low testosterone AND symptoms/signs 1. Document presence of:

Highly specific symptoms 2:

• Reduced libido and sexual activity
• Decreased spontaneous erections
• Loss of body/pubic/facial hair
• Hot flushes
• Reduced muscle bulk and strength
• Gynecomastia
• Very small or shrinking testes

Less specific but supportive symptoms 2:

• Decreased energy, motivation, initiative
• Depression or dysthymia
• Poor concentration and memory
• Sleep disturbance
• Mild anemia
• Increased body fat

Treatment Considerations

With testosterone this low (113 ng/dL) and confirmed symptoms, testosterone replacement therapy is strongly indicated 1. The goal is to raise serum testosterone into the mid-normal range 5.

Formulation Selection

Consider intramuscular testosterone enanthate or cypionate as first-line therapy 6. The 2020 American College of Physicians guideline suggests intramuscular over transdermal formulations because costs are considerably lower and clinical effectiveness and harms are similar 6.

Alternative options include 5:

• Transdermal gels
• Transdermal patches
• Testosterone pellets
• Injectable testosterone undecanoate

Monitoring on Treatment

Follow-up at 3-6 months, then annually 5:

1. Testosterone level at 3-6 months:

   • For injectable testosterone: measure midway between injections
   • Adjust if <400 ng/dL or >700 ng/dL 5
   • Target: mid-normal range

2. Hematocrit at 3-6 months, then annually:

   • Stop therapy if hematocrit >54% 5
   • Evaluate for hypoxia and sleep apnea
   • Reinitiate with reduced dose once safe

3. PSA and digital rectal exam (if age ≥40 and baseline PSA >0.6 ng/mL):

   • Check at 3-6 months
   • Then per age-appropriate screening guidelines 5
   • Obtain urology consultation if PSA increases >1.4 ng/mL within any period 5

4. Symptom assessment: Evaluate whether symptoms have improved 5

   • Discontinue if no improvement in sexual function after 12 months 6

Critical Pitfalls to Avoid

1. Do not diagnose during acute illness: Testosterone levels drop transiently with illness 2

2. Do not rely solely on total testosterone in older men or those with suspected SHBG abnormalities: Your free and bioavailable testosterone measurements are appropriately included 2, 7, 8, 9

3. Do not start treatment without confirming the diagnosis with a second morning measurement (though your level is so low this is unlikely to change) 1

4. Do not overlook fertility concerns: If you desire future fertility, this must be addressed before starting testosterone therapy, as it suppresses spermatogenesis 2

5. Do not miss secondary causes: Pituitary tumors, hemochromatosis, and other systemic diseases must be excluded 2