What is the likelihood of an STD causing sudden onset of low libido, ED, semen changes, and possible testicular atrophy in a male patient with abnormal hormone levels?

STD Likelihood and Hormonal Evaluation in Sexual Dysfunction

An STD is extremely unlikely to be the cause of this patient's symptoms given the hormonal profile showing markedly elevated total testosterone (45 nmol/L, reference 1-29) and SHBG (95 nmol/L, reference 1-47) with normal LH (7, reference 1-8.6) and FSH (9.5, reference 1-12). This pattern is inconsistent with sexually transmitted infections, which do not cause these specific hormonal abnormalities.

Why STDs Are Not the Primary Concern

• STDs do not cause elevated total testosterone or SHBG levels. The patient's total testosterone is approximately 55% above the upper limit of normal, which is incompatible with infectious etiologies 1.

• The hormonal pattern suggests a different underlying process. Normal LH and FSH with elevated total testosterone and SHBG indicates the hypothalamic-pituitary-gonadal axis is functioning, ruling out primary testicular failure that might occur with severe orchitis 1.

• STDs causing testicular involvement (orchitis) would present with low testosterone, elevated LH/FSH, acute testicular pain, and fever—none of which match this presentation 1.

The Actual Problem: Elevated SHBG

The patient's symptoms are most likely explained by elevated SHBG binding the testosterone, resulting in low free (bioavailable) testosterone despite high total testosterone levels 1.

Key Diagnostic Steps

• Measure free testosterone by equilibrium dialysis immediately. This is the critical missing test, as total testosterone can be misleadingly elevated when SHBG is high 1.

• A normal free testosterone level would explain the paradox of high total testosterone with hypogonadal symptoms (low libido, ED) 1.

• If free testosterone is low despite high total testosterone, this confirms SHBG is sequestering the hormone, making it biologically unavailable 1.

Differential Diagnosis for Elevated SHBG

The markedly elevated SHBG (double the upper limit) suggests:

• Chronic liver disease is the most important consideration, as hepatic dysfunction causes elevated SHBG, low free testosterone, and the exact symptom constellation described (ED, decreased libido, testicular atrophy) 1.

• Hyperthyroidism increases SHBG synthesis and should be evaluated with TSH and free T4 1.

• Obesity paradoxically can cause low SHBG, so this is less likely unless the patient has significant weight changes 1.

Testicular Atrophy Evaluation

"Possible testicular atrophy" requires objective measurement, not subjective assessment 2.

• Testicular volume should be measured with an orchidometer or ultrasound; volumes <10 cc indicate atrophy 3.

• In the context of normal FSH (9.5), significant testicular atrophy is less likely, as primary testicular failure typically elevates FSH above 12 1, 3.

• Testicular atrophy with normal FSH suggests either early disease or that the "atrophy" is subjective rather than pathological 4.

Semen Changes

Semen analysis is mandatory to objectively document changes 1.

• Look specifically for: volume, sperm concentration, motility, morphology, and presence of blood (hematospermia) 1.

• Hematospermia in men under 40 is typically benign and self-limited, but persistent cases warrant transrectal ultrasound 1.

• Oligospermia or azoospermia with normal FSH suggests obstructive causes or early spermatogenic failure 1, 4.

Immediate Workup Algorithm

1. Free testosterone by equilibrium dialysis (most critical test) 1
2. Comprehensive metabolic panel and liver function tests (AST, ALT, bilirubin, albumin, PT/INR) to evaluate for chronic liver disease 1
3. Thyroid function tests (TSH, free T4) 1
4. Prolactin level if free testosterone is low 1
5. Semen analysis 1
6. Testicular ultrasound to objectively measure testicular volume and assess for structural abnormalities 1, 3

STD Testing Considerations

While STD testing should still be performed as part of routine sexual health screening, it will not explain the hormonal abnormalities or symptom complex 1.

• Test for HIV, syphilis, gonorrhea, and chlamydia as standard practice, but these are not causing the elevated testosterone/SHBG 1.

• Chronic hepatitis B or C could explain elevated SHBG and sexual dysfunction, so include hepatitis serologies in the liver disease workup 1.

Common Pitfalls to Avoid

• Do not assume high total testosterone means the patient is "fine"—free testosterone is what matters clinically 1, 5.

• Do not attribute symptoms to "stress" or "psychological factors" without first measuring free testosterone 1.

• Do not overlook chronic liver disease, which can present insidiously with sexual dysfunction as the primary complaint 1.

• Do not rely on patient-reported testicular atrophy; objective measurement is essential 2.