Endocrine aspects of women’s sexual dysfunction: a focus on the role of Prolactin

Objective: Using the tools of Psychometric sexual testing, we wanted to investigate sexual function and distress in a clinical sample of premenopausal women with suspected prolactin abnormalities tested by TRH stimulation. In addition, we aimed at exploring cues for sexual desire in this study sample. Methods: Premenopausal women who came to our outpatient Gynecological Endocrinology Clinic at San Matteo Hospital, University of Pavia for evaluation of menstrual irregularities over a 3-year period (2017-2019). We had a series of 55 patients, but they were included according to the following criteria: 1) being Caucasian; 2) having mild menstrual irregularities (oligomenorrhea 35-60 days); 3) showing at least a recent blood testing indicating a possible derangement of PRL secretion with no evidence of ovulation at ultrasound evaluation and progesterone measurement; 4) being in a stable heterosexual relationship since at least 6 months; 5) having no history of major diseases, including psychiatric, overt eating and sleeping disorders, smoking, illicit drug use or symptoms of alcohol dependence; 5) willing to fulfill questionnaires regarding sexual function and behavior, after having signed an informed consent. Results: The most relevant clinical characteristics of our study population (n=34) presented an age range between 16-44 years (mean 27.8±7.4). Age at menarche was comprised between 10 and 15 years of age (Median 12; 95% CI for the median: 12-12.9). All women reported more than 13 years of education. Median BMI was 21.8 kg/m2 (95% CI for the median: 19.9-23.3). A pituitary adenoma was diagnosed by RMN in 35.3% (n=12) of our study sample Median baseline value of PRL was 18.5 ng/ml (95% CI for the median: 11.0-23.5). In 67.6% (n=23) PRL was in the normal range ≤ 25 ng/ml, in 17.6% (n=6) >25 and ≤ 50ng/ml and in 14.7% (n=5) > 50 ng/ml. Median baseline TSH was 1.7 mIU/L (95% CI for the median: 1.44-2.0). Mean FreeT3 was 3.45±0.7 pg/ml and median FreeT4 was 10.94 (95% CI for the median: 10.7-11.6). The majority of women (70.6 %; n=24) scored under the cut-off of normality for FSFI, whereas half of the sample (47.1%; n=16) displayed sexual distress. Women with pituitary adenoma scored for FSD in 80% of the cases (n=4/5), but they were significantly sexually distressed only in 20% (n=1/5) of the cases. In line with the profile of PRL response after TRH test in women with and without FSD, the rate of increase of PRL following TRH bolus showed a non-significant trend to be higher at 30 and 60 minutes. The analysis of AUC for PRL did not add any relevant information regarding the diagnosis of both FSD and sexual distress. The pattern of release of plasma TSH after TRH administration was similar in women with and without FSD or sexual distress, as shown by MANOVA. the analysis of cues for sexual desire displayed a peculiar profile according to the PRL categories, being globally significantly lower (F=4.8; p=.01) in women with PRL > 50 mg/ml diagnosed with pituitary adenoma (Figure 9). The poor reporting of sexual cues was highly significant for explicit/erotic (F=6.0; p=.006) (Figure 10) and even for visual/proximity (F=4.1; p=.02). Finally, it was interesting to observe that a lower amount of PRL released following TRH test (AUC) is positively associated (R=.423; p=.01) with a significantly higher number of visual/proximity sexual cues. Conclusions: Even if not conclusive, our results confirmed that PRL levels should be always taken into account when evaluating the biomedical etiologies of female sexual dysfunction. Indeed, prolactin plays a crucial role in the biopsychococial model able to interpreter sexual concerns of women in the intra-personal and inter-personal context and may offer some clues for therapeutic interventions. Further studies in larger samples are mandatory to elucidate the involvement of prolactin as a sexual hormone linking stress and reproductive function.