The disorder of desire is less frequent in male rather than female and usually increases with age. Sexual desire or arousal consists of the mind‘s processing of internal sexual stimuli and external stimuli and their context. It is the first phase of the normal sexual response that predisposes complex brain circuitries involving those cortical, limbic and paralimbic regions known to be associated with cognition, emotion and motivation. These circuitries mediate the right sex-seeking behaviors and modulate the autonomic nervous system of lumbosacral regulating erection and ejaculation phase. Therefore, many psychological, neurological and local factors could determine an altered sexual desire.
Pathologically the disorders of desire can be distinguished into an increasing or a reduced sexual desire, and in an altered sex-seeking behavior.
The most common disorder of desire is by far the Hypoactive Sexual Desire also called hyposexuality, that is defined as a persistently or recurrently deficient (or absent) sexual fantasy and desire for sexual activity leading to marked distress or interpersonal difficulty.
The diagnosis of primary desire loss in men can only be made after eliminating the presence of factors known to affect the sexual function. Thus major psychiatric disorders, chronic medical conditions, intake of pharmacological agents, or substance abuse have to be excluded.
Disorders of sexual desire are mainly caused by psychogenic factors and androgen deficiency. Psychogenic conditions leading to a desire deficiency state in men include psychiatric illness such as depression or psychosis, preoccupation with life crisis or grief, gender identity conflicts and aging-related psychological issues.
A particular form of psychogenic desire disorder is termed “excitement inhibition”. It is commonly seen in patients who have sexual drive but cannot maintain excitement with performance anxiety due to the fear of sexual failure and the vigilant preoccupation with erection during lovemaking.
The other common form of Hypoactive Sexual Desire is due to a low blood androgens concentration. A critical level of blood androgens is required for the maintenance of normal sexual desire, even if it is still a controversial debate. Nevertheless, in hypogonadic state there is some evidence of Hypoactive Sexual Desire, but the concentration of testosterone required for maintaining libido is lower than for supporting spermatogenesis and growth and function of prostate and seminal vesicles.
Also patients with a central nervous system disease such as Epilepsy, Parkinsonism, Stroke and Adrenoleukodystrophy may have a diminished sexual arousal. The pathogenesis of loss of desire in these neurological disorders appears to be multifactorial in origin and includes disease-related hormone abnormalities, physical restrictions and reduced well-being.
Finally, several pharmacological agents (mainly antihypertensive and psychiatric medications) or substances of abuse could potentially induce hyposexuality through different mechanisms of action which will be better explained elsewhere.
Hyper sexuality, also called compulsive sexual behavior, is characterized by inappropriate or excessive sexual cognition or behavior that lead to subjective distress or impaired functioning in one or more important life domains. Psychiatric illnesses are considered to be the most frequent cause of abnormal sexual behavior, but many neurological disorders can interfere with a right sexual behavior especially the degenerative ones such as Parkinson, Alzheimer diseases.