Sexual Dimorphism
Several hypothalamic nuclei are sexually dimorphic, i.e. there are clear differences in both structure and function between males and females.
Some differences are apparent even in gross neuroanatomy: most notable is the sexually dimorphic nucleus within the preoptic area. However most of the differences are subtle changes in the connectivity and chemical sensitivity of particular sets of neurons.
The importance of these changes can be recognised by functional differences between males and females. For instance, males of most species prefer the odor and appearance of females over males, which is instrumental in stimulating male sexual behavior. If the sexually dimorphic nucleus is lesioned, this preference for females by males diminishes. Also, the pattern of secretion of growth hormone is sexually dimorphic, and this is one reason why in many species, adult males are much larger than females.
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