Prevalence of Prolactinoma in Men with Hypogonadism
The available evidence does not provide a direct answer to what percentage of men with hypogonadism have a prolactinoma, as the provided studies examine the reverse relationship—the prevalence of hypogonadism in men with prolactinomas rather than the prevalence of prolactinomas among men with hypogonadism.
What the Evidence Shows (Reverse Relationship)
Approximately 80% of men with prolactinomas present with hypogonadism at diagnosis 1, 2, 3. This represents the proportion of men who have prolactinomas and subsequently develop hypogonadism, not the proportion of hypogonadal men who have prolactinomas.
Key Clinical Context
Men with prolactinomas typically present with macroadenomas (70% of cases) and hypogonadism is their most common presenting feature 4.
In men with prolactinomas, hypogonadism manifests as:
Hyperprolactinemia is found in 16% of men presenting with erectile dysfunction and approximately 11% of men with oligospermia 5, suggesting that prolactinomas represent a meaningful but minority cause of male hypogonadism.
Clinical Implications for Evaluation
When evaluating men with hypogonadism, prolactin measurement should be performed to screen for prolactinoma, particularly in those presenting with 6:
- Sexual dysfunction (loss of libido, erectile dysfunction)
- Visual field defects or headaches
- Galactorrhea (present in 8% of men with prolactinomas) 4
- Gynecomastia (present in 23% of men with prolactinomas) 4
Diagnostic Thresholds
Prolactin levels in men with prolactinomas typically exceed 4,000 mU/L (188 μg/L), with median levels around 20,000 mU/L 6, 4.
Serial dilutions should be performed in men with large pituitary lesions but paradoxically normal or mildly elevated prolactin to detect the "high-dose hook effect" 6, 7.
Important Caveats
The question cannot be definitively answered from the available evidence because:
The provided studies focus on pediatric/adolescent populations or examine prolactinoma patients rather than unselected hypogonadal men [6-6].
Population-based studies examining the prevalence of prolactinomas among all men with hypogonadism are not included in the evidence provided.
Hypogonadism has multiple etiologies (primary testicular failure, other pituitary disorders, obesity, medications, aging), and prolactinomas represent only one potential cause 2, 5.