The interstitial nuclei of the human anterior hypothalamus: an investigation of variation with sex, sexual orientation, and HIV status.
Level 4 - case-series / case-control
Postmortem observational cross-sectional case-control study
PubMed 11534967 · doi:10.1006/hbeh.2001.1680
What was done
Researchers measured the volume, neuronal size, neuronal density, and neuron numbers in the interstitial nuclei of the human anterior hypothalamus (INAH1–4) using Nissl-stained coronal sections from autopsy tissue. The cohort comprised 34 presumed heterosexual men (24 HIV-negative, 10 HIV-positive), 34 presumed heterosexual women (25 HIV-negative, 9 HIV-positive), and 14 HIV-positive homosexual men (total n = 82).
What was found
HIV status significantly influenced INAH1 volume (8% larger in HIV-positive heterosexual men and women compared to HIV-negative individuals), but had no effect on INAH2–4. INAH3 had significantly greater volume and significantly more neurons in presumed heterosexual men than in women. No other sex differences in volume were detected, and no sexual variation in neuronal size or density was found for any INAH. There was a trend toward smaller INAH3 volume in homosexual men compared to heterosexual men, but no difference in the total number of INAH3 neurons. Absolute volumes, neuron counts, and p-values were not reported in the abstract.
Why it matters
The study confirms sex differences in INAH3 volume and neuron number while providing evidence that volumetric variations associated with sexual orientation are not accompanied by differences in total neuron count.
Limits
All homosexual subjects were HIV-positive, confounding sexual orientation with disease status. Heterosexual orientation was presumed rather than directly verified. The sample size for homosexual men was small (n = 14), and exact numerical data and confidence intervals are not provided in the abstract.
Cited by
- partial William Byne's group independently replicated the finding that the INAH3 nucleus is smaller in homosexual men compared to heterosexual men.