What is the appropriate evaluation and management for a male patient with suppressed FSH (Follicle-Stimulating Hormone) and LH (Luteinizing Hormone) levels, normal total testosterone, and mildly elevated prolactin levels?

Evaluation and Management of Suppressed FSH/LH with Normal Testosterone

This patient requires immediate investigation for exogenous testosterone use or testosterone-secreting tumors, as the combination of suppressed gonadotropins (FSH <0.3, LH <0.3) with normal-to-high testosterone (753 ng/dL) indicates either exogenous androgen administration or autonomous testosterone production. 1

Critical Diagnostic Approach

First Priority: Rule Out Exogenous Testosterone

• Directly question the patient about testosterone supplementation, anabolic steroids, or performance-enhancing substances, as this is the most common cause of this hormonal pattern 1
• Exogenous testosterone suppresses the hypothalamic-pituitary-gonadal axis through negative feedback, causing profound suppression of both FSH and LH while maintaining elevated testosterone levels 2, 3
• Injectable testosterone causes FSH suppression by 86.3% and LH suppression by 71.8%, while transdermal preparations cause FSH suppression by 60.2% and LH suppression by 59.2% 4

Second Priority: Evaluate for Testosterone-Secreting Tumors

• Perform testicular examination and scrotal ultrasound to evaluate for testicular masses if exogenous use is denied 1
• Obtain adrenal imaging (CT or MRI) to exclude testosterone-secreting adrenal tumors 1
• Measure DHEA-S levels to help differentiate adrenal from testicular sources of androgen excess 1

Prolactin Assessment

• The prolactin level of 5.1 ng/mL is within normal range (typically <15-20 ng/mL) 5
• While the AUA guideline recommends measuring prolactin in patients with low testosterone and low/normal LH to screen for hyperprolactinemia 5, this patient's normal testosterone makes prolactinoma unlikely
• Repeat prolactin measurement is not urgently needed unless it was initially elevated, as persistently elevated prolactin would warrant endocrinology referral and pituitary MRI 5

Management Based on Findings

If Exogenous Testosterone Use Confirmed:

• Counsel on immediate cessation and explain risks including polycythemia, cardiovascular concerns, and suppression of endogenous testosterone production 1
• Testosterone therapy is strongly contraindicated in eugonadal men per European Association of Urology guidelines 1
• Monitor for recovery of the hypothalamic-pituitary-gonadal axis after cessation, which typically takes 3-6 months 1
• The negative feedback mechanism remains intact even in men with hypothalamic-pituitary disease, so recovery is expected once exogenous testosterone is discontinued 3

If Tumor Identified:

• Refer to urology or endocrinology for surgical evaluation of testicular masses 1
• Refer to endocrinology for management of adrenal tumors 1
• Do not assume elevated testosterone is benign without investigation, as testosterone-secreting tumors can have significant morbidity if undiagnosed 1

If No Clear Etiology Found:

• Consider pituitary MRI if testosterone levels are markedly elevated or if there are other concerning features, though the AUA guideline specifically recommends this for testosterone <150 ng/dL with low/normal LH 5
• Refer to endocrinology for further evaluation of this atypical hormonal pattern 5

Critical Pitfalls to Avoid

• Do not prescribe testosterone therapy based solely on symptoms when testosterone levels are normal or elevated, as approximately 25% of men receiving testosterone do not meet criteria for deficiency 1
• The AUA defines testosterone deficiency as total testosterone below 300 ng/dL on two separate early morning measurements 5, and this patient's level of 753 ng/dL is well above this threshold
• Do not assume this hormonal pattern is benign without thorough investigation for exogenous use or tumors 1
• The combination of suppressed gonadotropins with normal testosterone is physiologically inappropriate and always requires explanation 5