Sexual desire is the most elusive dimension of human sexuality. It is therefore difficult to define and measure, first and foremost due to uncertain parameters regarding what should be considered normal.
According to Spinoza, "desire is the sadness due to the lack of what we love". There are three aspects in this philosophical but also poetic definition: the sense of lack and distance, sadness and love. The definition of Spinoza reminds us of how difficult it is to talk about desire without talking about love. This is particularly apparent in the feminine perception of desire, in which the emotional dimension of intimacy is perceived as equally and sometimes more important than the physical one.
There is no "center" of sexual desire, but this is the result of complex interactions between rhinencephalon, limbic lobe and neocortex. The integrity of the central nervous system and the limbic - medullary axis (back - lumbar center, sacral center) as well as the integrity of pelvic structures and genital organs are necessary for normal sexual behavior.
Recent research has shown that the neurotransmitters most involved in sexuality are dopamine with a stimulant function, and serotonin, with its inhibitory function.
Variations in sexual behavior may be triggered by alterations in the levels of steroids present during the various phases of the reproductive cycle. Numerous studies also document an enhancement of sexual desire and ease of orgasm in woman in the middle of the reproductive cycle. Cultural and psychological conditioning means that sexual desire in the human species is present in all phases of the cycle (Dei M et al Eur Journal Contracep Reprod Health Care 2; 1997).
Estrogen: modulates ovulation feedback and sexual behavior, affecting general and genital somatic trophism, essential for good sexual function.
Androgens are physiologically secreted in minimal quantities by Leydig cells that are persistent at ovarian level, under the influence of luteinizing hormone (LH) with a peak precisely in the ovulatory phase. The biological meaning of the peak is twofold: it accentuates sexual receptivity and promotes the atresia of the follicles. Androgens would play a predominant role in the mechanisms linked to desire and excitement
Prolactin has a predominantly inhibitory role in both sexes. Chronically stressful situations, some psycho-drugs, the presence of pituitary microadenomas are associated with an increase in blood values and may result in a decrease in sexual desire.
Oxytocin is a neurohormone that has a peak plasma concentration that coincides with orgasm: it would be the facilitator responsible for the sense of satiety and act as facilitator of the "homeostatic" function of sexual desire.