Although we are still far from knowing exactly where and how the pineal suppressive role is exerted, the fact that the gland exerts an inhibitory function on the reproductive axis is widely accepted. In fact, the pineal seems to exert its hormonal effect at different levels of the reproductive axis, both at the hypothalamic-pituitary level and at the gonadal level, where melatonin receptors have also been found.
Furthermore, melatonin appears to increase prolactin secretion, which may contribute to sexual dysfunction. Based on the observations mentioned above a group of italian investigators hypothesized that an inhibition of pineal gland activity via a treatment with bright light could favorably influence sexual function and pilot tested the usefulness of bright light therapy in a small sample of 9 male patients with nonorganic sexual dysfunction. Subjects (age 39-60) were consecutively recruited in the outpatient clinic of the Urology Department of the University of Siena Medical Center on the basis of a diagnosis of primary (i.e. not due to another illness or to a medication or a drug of abuse) hypoactive sexual desire disorder (HSDD, n = 2), sexual arousal disorder (SAD, n = 6), and orgasmic disorder (OD, n = 1) and the absence of a mood disorder, as assessed via the Mini International Neuropsychiatric Interview. Subjects were randomly assigned to active light treatment (ALT) or placebo light treatment (L-PBO) and assessed at baseline and after 2 weeks of ALT/L-PBO treatment via the Structured Clinical Interview for DSM-IV-Sexual Disorders (SCID-S) and via a sexual satisfaction self-report, which asked them to rate on a scale from 1 to 10 their level of sexual satisfaction.