What laboratory tests should be ordered for a 30-year-old male with low sex drive, depression, and currently taking sertraline (Selective Serotonin Reuptake Inhibitor, SSRI) 50mg?

Laboratory Tests for Low Sex Drive in a 30-Year-Old Male with Depression on Sertraline

For a 30-year-old male with low sex drive who is taking sertraline 50mg for depression, serum total testosterone should be measured as the primary laboratory test, along with glucose/HbA1c and lipid profile to evaluate for metabolic factors affecting sexual function. 1

Primary Laboratory Evaluation

• Serum total testosterone: Essential first-line test for all men with sexual dysfunction

  • Should be drawn in the morning when levels are highest
  • Target level: >300 ng/dL is considered normal
  • If borderline or low, repeat to confirm

• Metabolic screening:

  • Fasting glucose or HbA1c
  • Lipid profile (total cholesterol, HDL, LDL, triglycerides)

Secondary Laboratory Tests (if indicated)

• Free or bioavailable testosterone: Particularly important in obese patients or those with conditions affecting sex hormone-binding globulin (SHBG) 2

• Sex hormone-binding globulin (SHBG): To calculate free testosterone index if total testosterone is borderline normal but symptoms persist

• Luteinizing hormone (LH) and follicle-stimulating hormone (FSH): To distinguish between primary and secondary hypogonadism if testosterone is low

Rationale for Testing

Sexual dysfunction in this case likely has multiple contributing factors:

1. Medication effect: Sertraline (SSRI) is strongly associated with sexual dysfunction, including decreased libido in 6% of patients compared to 1% on placebo 3. Studies show that 62.9% of patients on sertraline experience some form of sexual dysfunction 4.

2. Hormonal factors: Testosterone deficiency can cause decreased libido independent of or in addition to SSRI effects.

3. Metabolic factors: Conditions like diabetes and hyperlipidemia can contribute to sexual dysfunction and should be ruled out.

4. Depression itself: The underlying depression may contribute to decreased libido regardless of medication.

Clinical Considerations

• The American Urological Association (AUA) guidelines specifically state: "Serum total testosterone should be measured in all men with ED to determine if testosterone deficiency (TD), defined as total testosterone <300 ng/dL with the presence of symptoms and signs, is present." 1

• While the primary complaint is low sex drive rather than erectile dysfunction, the same laboratory evaluation applies as these conditions often overlap.

• SSRIs like sertraline are known to cause sexual dysfunction through multiple mechanisms, with studies showing significantly higher rates of sexual dysfunction (63% in men) compared to other antidepressants like bupropion (15%) 5.

Management Implications

The laboratory results will guide management options:

• If testosterone is low: Consider testosterone replacement therapy if there are no contraindications
• If metabolic abnormalities are present: Address underlying conditions
• If all labs are normal: Consider medication adjustment (dose reduction, drug holiday, or switching to an antidepressant with lower sexual side effect profile like bupropion)

Remember that sertraline-induced sexual dysfunction often manifests early in treatment (as early as day 7) and may persist throughout treatment 5, so addressing this issue promptly is important for medication adherence and quality of life.