What can cause testicular atrophy (shrinkage) with high Sex Hormone-Binding Globulin (SHBG) and total testosterone levels, normal Luteinizing Hormone (LH) levels, and no varicocele or infection present?

Testicular Atrophy with High SHBG, High Total Testosterone, and Normal LH

Your hormone profile (high SHBG, high total testosterone, normal LH at 7.0 IU/L) does not cause testicular atrophy, and the most likely explanations for progressive testicular shrinkage in your case are idiopathic lymphocytic orchitis (especially given your history of testicular pain that has since resolved), subclinical trauma, or early testicular dysgenesis that your ultrasound may have missed. 1, 2

Understanding Your Hormone Profile

Your specific hormone pattern argues strongly against primary testicular failure as the cause of shrinkage:

• Normal LH (7.0 IU/L) indicates your pituitary-testicular axis is functioning appropriately - if your testes were failing, LH would be elevated (typically >10-12 IU/L) as your pituitary tries to compensate 1, 3
• High SHBG does not impair sperm production or testicular size because spermatogenesis depends on intratesticular testosterone (ITT), which is maintained by LH stimulation of Leydig cells independent of circulating SHBG levels - ITT concentrations are 50-100 times higher than serum levels 3
• High total testosterone with normal LH suggests your Leydig cells are functioning well, making primary testicular dysfunction unlikely 3

Most Likely Causes of Testicular Shrinkage in Your Case

Idiopathic Lymphocytic Orchitis

• This is a rarely reported but important cause of testicular atrophy that presents with testicular pain followed by progressive shrinkage - the pain you experienced may have been the inflammatory phase 2
• Conventional investigations (ultrasound, infection workup) are typically unremarkable, which matches your presentation 2
• Diagnosis requires testicular biopsy showing lymphocytic infiltration with reduced spermatogenesis 2

Subclinical Trauma

• Testicular atrophy occurs in 50% of patients following blunt scrotal trauma, even when the initial injury seems minor 4
• The pain you experienced could have been from an injury you don't recall or considered insignificant 4
• Atrophic testes from trauma can appear homogeneous and normal on ultrasound in 30% of cases, or show heterogeneous echogenicity with reduced blood flow in 50% of cases 5, 4

Early Testicular Dysgenesis

• Non-homogeneous testicular architecture on ultrasound represents testicular dysgenesis and impaired spermatogenesis - however, your ultrasound was reportedly normal 1
• A slightly smaller testis with normal vascularity and normal ultrasound structure does not indicate permanent dysfunction and should be reassuring 1

Critical Next Steps

Immediate Evaluation

• Obtain a complete semen analysis (two samples, 2-3 months apart) - this is the definitive test to assess actual fertility status, as ultrasound findings are suggestive but not diagnostic 1, 3
• Measure FSH levels - if FSH is >7.6 IU/L with testicular atrophy, this suggests non-obstructive azoospermia and primary testicular dysfunction 3, 6
• Check free testosterone or calculate free testosterone index using your total testosterone and SHBG to determine bioavailable testosterone 3
• Evaluate thyroid function (TSH, free T4) - thyroid disorders commonly affect reproductive hormones and can cause SHBG elevation 3

Advanced Imaging Consideration

• Request a repeat scrotal ultrasound with specific attention to testicular architecture (homogeneous vs. heterogeneous), blood flow on Doppler, and presence of microcalcifications 1, 5
• Testicular microcalcifications are associated with an 18-fold higher prevalence of testicular cancer in infertile men and correlate with spermatogenic dysfunction 7, 1

If Atrophy Progresses or FSH Becomes Elevated

• Consider testicular biopsy to diagnose lymphocytic orchitis or testicular dysgenesis - this is particularly important if you develop severe atrophy (<12 mL volume) combined with structural abnormalities 1, 2
• Genetic testing (karyotype analysis and Y-chromosome microdeletion testing) should be performed if semen analysis shows severe oligospermia (<5 million/mL) or azoospermia 3

Important Reassurances and Caveats

What Your Normal Ultrasound Means

• A normal ultrasound 2 months ago with normal vascularity and homogeneous architecture is genuinely reassuring - severe atrophy typically shows non-homogeneous architecture, reduced blood flow, or volume <12 mL 1, 5
• However, ultrasound cannot detect early lymphocytic orchitis or subtle testicular dysgenesis in all cases 2, 5

Fertility Preservation

• If semen analysis confirms oligospermia or declining sperm counts, strongly consider sperm cryopreservation immediately as a protective measure 3
• Even if FSH becomes elevated and testicular atrophy progresses, up to 50% of men with non-obstructive azoospermia have retrievable sperm with microsurgical testicular sperm extraction (micro-TESE) 1, 3, 6

Critical Pitfall to Avoid

• Never start exogenous testosterone therapy if fertility is a concern - it will completely suppress LH and FSH through negative feedback, eliminating intratesticular testosterone production and causing azoospermia that can take months to years to recover 3

Addressing Reversible Factors

• Optimize any metabolic factors - weight normalization and metabolic optimization may improve hormonal parameters in some cases 3
• Correct thyroid dysfunction if present - thyroid disorders disrupt the hypothalamic-pituitary-gonadal axis and should be evaluated and corrected 3

When to Worry vs. When to Be Reassured

Reassuring features in your case:

• Normal LH indicates appropriate pituitary-testicular signaling 1, 3
• Normal ultrasound 2 months ago with no structural abnormalities 1
• No varicocele present 7
• Pain has resolved (though this could indicate the inflammatory phase of orchitis has passed) 2

Concerning features requiring close monitoring:

• Progressive shrinkage over one year despite normal hormones 6, 2
• History of testicular pain (even if resolved) suggests inflammatory or traumatic etiology 2, 4
• Subjective perception of ongoing shrinkage warrants objective measurement 1, 5