Are gender identity and sexual orientation determined prenatally or do postnatal social factors play any role? These are some intriguing questions which demand more clarity. With the growing dilemma around gender identity and disputes regarding sexual dysphoria, many neuropsychologists have focused their research on studying the areas of the brain that govern and orchestrate these functions. One such area that has gained immense attention in the recent past is the sexual dimorphic nucleus of preoptic area (SDN-POA) in hypothalamus. Our descriptive review was aimed to coalesce the existing information about the human preoptic nucleus location, its anatomical description and dimorphic changes in both sexes. We have broadened our search spectrum to encompass deeper insights into the role of SDN-POA in sex regulation, orientation and sexual or gender identity. Relevant articles were obtained by a comprehensive search conducted through PubMed, Scopus, Embase and google scholar electronic database. The search was employed using keywords related to hypothalamus, medial preoptic nucleus, sexually dimorphic nucleus, and sex regulation. The review includes English language articles published between January 1980 and July 2023. With compiled data from all the published human and non-human studies, we could relatively conclude that the existing research has given ample evidence about the sexual dimorphic changes seen in SDN-POA during brain development and with aging, among sexes. Males showed larger area and neuronal size in comparison to females. Despite comprehensive review, ambiguity still persists with regards to its anatomical nomenclature, location and its function. We found it increasingly difficult to construct a clear outline of the region and establish its connection with gender identity or orientation as hypothesized by previous authors. Nevertheless, the existing body of literature offers a foundational collation of knowledge, encouraging further investigation as we continue to seek clearer answers about the region’s role in the neurobiology of sexual orientation.
Keywords: Hypothalamus, Uncinate nucleus, Medial preoptic nucleus, Sexually dimorphic nucleus, Anterior hypothalamic nuclei, Sexual orientation.
