A difference in hypothalamic structure between heterosexual and homosexual men.
Level 4 - case-series / case-control
Postmortem cross-sectional comparative study
PubMed 1887219 · doi:10.1126/science.1887219
What was done
Postmortem brain tissue was examined to measure the volumes of four cell groups in the anterior hypothalamus—interstitial nuclei of the anterior hypothalamus 1, 2, 3, and 4 (INAH 1–4)—across three subject groups: women, men presumed to be heterosexual, and homosexual men.
What was found
No volume differences were found between groups for INAH 1, 2, or 4. INAH 3 was more than twice as large in heterosexual men as in women, and more than twice as large in heterosexual men as in homosexual men. Exact volume measurements, sample sizes, and dispersion metrics were not reported in the abstract.
Why it matters
This study provided early neuroanatomical evidence that sexual orientation in men correlates with structural dimorphism in the anterior hypothalamus, suggesting a biological substrate.
Limits
The abstract does not report the sample size, participant demographics, or quantitative volume values. Sexual orientation in the heterosexual male group was presumed rather than confirmed. Cross-sectional postmortem studies cannot establish whether anatomical differences are congenital, causal, or secondary to behavioral, hormonal, or disease-related factors.
Cited by
- supports Simon LeVay found that the third interstitial nucleus of the anterior hypothalamus (INAH3 / SDN-POA) is significantly smaller in gay men than in straight men and comparable in size to that in women.