How to manage low testosterone levels with low Follicle-Stimulating Hormone (FSH) levels after pituitary removal?

Management of Low Testosterone with Low FSH Levels After Pituitary Removal

Testosterone replacement therapy is the primary treatment for patients with low testosterone and low FSH levels following pituitary removal, with careful monitoring of hormone levels and consideration of fertility needs.

Diagnostic Evaluation

Before initiating treatment, a comprehensive hormonal assessment should include:

• Morning total testosterone (drawn between 8-10 AM)
• Free testosterone by equilibrium dialysis
• Sex hormone-binding globulin (SHBG)
• Luteinizing hormone (LH) and FSH levels
• Consider MRI of the sella turcica if not already performed 1

Treatment Algorithm

Step 1: Confirm Secondary Hypogonadism

• Low testosterone with low/normal LH and FSH confirms secondary hypogonadism due to pituitary insufficiency 2
• Rule out other causes of hypogonadism

Step 2: Assess Fertility Desires

• For patients desiring fertility:

  • Human chorionic gonadotropin (hCG) injections should be initiated instead of testosterone replacement 3
  • Consider adding FSH injections if spermatogenesis is not achieved with hCG alone 3
  • This approach can promote testicular growth and spermatogenesis in approximately 80% of patients 3

• For patients not concerned about fertility:

  • Proceed with testosterone replacement therapy 2

Step 3: Select Appropriate Testosterone Formulation

• Transdermal testosterone preparations (gel or patch) are generally preferred as first-line options because:

  • They provide more stable day-to-day testosterone levels
  • Lower risk of erythrocytosis (15.4% or less) compared to injectable formulations (43.8%) 2
  • Target serum testosterone range: 450-600 ng/dL 2

• Injectable testosterone options:

  • Consider if cost is a concern or patient preference
  • Note that longer-acting injectables cause greater suppression of FSH (86.3%) and LH (71.8%) compared to transdermal preparations 4

Monitoring Protocol

1. Initial follow-up: 1-2 months after starting treatment 2
2. Subsequent monitoring: Every 3-6 months for the first year, then yearly 2
3. Testosterone levels: Test 2-3 months after treatment initiation or dose change 2
4. Parameters to monitor:
   • Total testosterone (target: 450-600 ng/dL)
   • Hematocrit (discontinue if >54%)
   • PSA (refer for biopsy if >4.0 ng/mL or increases >1.0 ng/mL in first six months)
   • Bone mineral density
   • Lipid profile
   • Liver function tests 2

Special Considerations

Multiple Pituitary Hormone Deficiencies

• Evaluate for other pituitary hormone deficiencies (ACTH, TSH, GH) 1
• Critical: Always start corticosteroid replacement several days before thyroid hormone replacement to prevent adrenal crisis 1
• Consider growth hormone deficiency assessment 6-12 months after pituitary surgery 1

Potential Complications

• Monitor for gynecomastia, which is a common side effect of gonadotropin therapy 3
• Be aware that testosterone therapy can mask ongoing pituitary dysfunction by suppressing gonadotropins 5

Treatment Success Factors

• Higher baseline testicular volume predicts better response to therapy 3
• Higher baseline inhibin B serum concentrations correlate with better outcomes 3
• Patients with post-pubertal onset of hypogonadism generally have better therapeutic success 3

Important Caveats

• Testosterone replacement will further suppress already low FSH and LH levels 5
• Higher gonadotropin levels during testosterone replacement decrease the chance of achieving eugonadism 5
• Patients should receive education on the importance of adherence to treatment and regular monitoring 2
• Testosterone is a controlled substance (CIII) and should be stored securely 6

By following this structured approach, patients with low testosterone and low FSH levels after pituitary removal can achieve optimal hormonal balance and improved quality of life.