Can STIs Cause Sudden Low Libido, ED, Semen Changes, and Testicular Atrophy?
STIs are not a primary cause of this symptom constellation—you need urgent evaluation for hypogonadism (testosterone deficiency), which universally causes these symptoms when severe. While certain STIs can cause epididymitis and testicular inflammation, they do not typically present with the combination of sudden low libido, erectile dysfunction, semen changes, AND testicular atrophy together 1, 2.
Why STIs Are Unlikely to Be the Primary Cause
Testicular atrophy specifically points away from acute infection. Testicular atrophy develops from chronic hormonal dysfunction, not from sexually transmitted infections 1. When STIs affect the male reproductive tract, they cause:
- Acute epididymitis or epididymo-orchitis with scrotal pain, swelling, and redness developing over 1-2 days—not gradual atrophy 1
- Urethral discharge or dysuria as primary symptoms, not isolated libido changes 1
- Focal testicular tenderness rather than bilateral atrophy 1
The European Association of Urology guidelines explicitly state that sexual partners of patients with accessory sex gland infections caused by STIs should be referred for evaluation, but this recommendation applies when infection is confirmed—not when the presentation suggests hormonal dysfunction 1.
What Actually Causes This Symptom Pattern
Hypogonadism (low testosterone) universally causes diminished libido when significantly suppressed and is strongly associated with erectile dysfunction, oligospermia, and testicular atrophy 1, 2. The American Association for the Study of Liver Diseases describes how low testosterone results in "erectile dysfunction, oligospermia, testicular atrophy, and feminization" through suppression of the hypothalamic-pituitary axis 1.
Primary Diagnostic Steps You Need Now
Measure morning total testosterone (between 8-10 AM) on two separate occasions—this is mandatory 1, 2, 3. The threshold is <300 ng/dL for considering testosterone deficiency 2, 4.
- If testosterone is low, measure LH and FSH to distinguish testicular failure (primary hypogonadism with elevated LH/FSH) from pituitary/hypothalamic dysfunction (secondary hypogonadism with low-normal LH/FSH) 1, 4
- Measure prolactin if testosterone is low OR if loss of libido is the primary complaint—elevated prolactin universally causes reduced libido 2, 3
- Free testosterone or androgen index is preferred over total testosterone alone, as this prevents unnecessary investigation in up to 50% of men with low total testosterone 2, 5
Additional Critical Evaluations
Check fasting glucose or HbA1c to exclude diabetes, which causes sexual dysfunction through vascular and neurological mechanisms 2, 3.
Review all medications immediately—beta-blockers, SSRIs (paroxetine, sertraline, citalopram, fluoxetine), antipsychotics, 5-alpha reductase inhibitors (finasteride, dutasteride), and opioids all commonly cause this exact symptom pattern 2.
When to Consider Infection
STI testing is appropriate if you have:
- Urethral discharge, dysuria, or scrotal pain/swelling 1
- New sexual partners with risk factors 1
- Acute onset scrotal symptoms (pain, redness, swelling over hours to 1-2 days) rather than gradual atrophy 1
The ACR Appropriateness Criteria state that epididymitis has a more insidious and gradual onset than testicular torsion, but still presents with scrotal pain as the primary feature—not isolated libido changes 1.
Critical Pitfall to Avoid
Do not delay hormonal evaluation while pursuing infectious workup. Testicular atrophy with low libido and ED represents hormonal dysfunction until proven otherwise 1, 2. A study of 508 men with sexual dysfunction found that 15.6% had hypogonadism, and a history of decreased libido or testicular atrophy could not predict these cases—meaning you cannot rely on clinical impression alone 5.
Hypogonadism is present in approximately 36% of men seeking consultation for sexual dysfunction, making it far more common than STI-related testicular pathology in this presentation 4.
Immediate Action Algorithm
- Obtain two morning testosterone measurements (8-10 AM) 2, 4, 3
- If testosterone <300 ng/dL: measure LH, FSH, and prolactin 1, 2, 4
- Screen for diabetes with fasting glucose or HbA1c 2, 3
- Review medication list for sexual dysfunction-causing drugs 2
- Consider STI testing only if urethral symptoms, discharge, or acute scrotal pain present 1
The combination of testicular atrophy, low libido, ED, and semen changes demands endocrine evaluation first—this is not the typical presentation of sexually transmitted infection 1, 2.