الفهرس 
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Abstract
Summary : Traditionally, testosterone and estrogen have been considered to be male and female sex hormones, respectively. However, estradiol, the predominant form of estrogen, also plays a critical role in male sexual function. Estradiol in men is essential for modulating libido, erectile function, and spermatogenesis. Estrogen receptors, as well as aromatase, the enzyme that converts testosterone to estrogen, are abundant in brain, penis, and testis, organs important for sexual function. In the brain, estradiol synthesis is increased in areas related to sexual arousal. In addition, in the penis, estrogen receptors are found throughout the corpus cavernosum with high concentration around neurovascular bundles. Low testosterone and elevated estrogen increase the incidence of erectile dysfunction independently of one another. In this study, we first measured the levels of the serum sex hormones (total T, free T and E2) in both normal controls and old men complaining of low sexual desire, and observed whether the T or free T/E2 ratio is imbalanced in cases of low sexual desire in ageing men. The present study was conducted on 50 low sexual desire old men and 40 healthy control men. Their mean age was 59.8 (55-69) years. The results revealed the following : 1. There was a significant difference between the two groups regarding the mean serum levels of E2, and there was a significant difference between the two groups regarding the mean serum levels of prolactin, SHBG, TT, TT/E2, FT and FT/E2. 2. In study group; TT/E2 showed significantly positive correlation with serum TT and significant negative correlation with serum E2. Serum FT showed significant positive correlation with IIFE5, sexual desire and SDI-2. ; FT/E2 showed significant positive correlation with IIEF, sexual desire, SDI-2, TT/E2. Additionally, serum FT showed significant negative correlation with serum E2. 3. In control group; SHBG showed a significant positive correlation with SDI-2, prolactin. E2 showed a significant negative correlation TT; TT/E2 showed a significant positive correlation with TT and showed a significant negative correlation with E2. FT showed a significant positive correlation with IIEF and SDI-2. Additionally, FT/E2 showed a significant positive correlation with SDI-2, prolactin, TT/E2. 4. SHBG, E2, TT/E2 showed poor AUCs (AUC=0.651, 0.626, 0.685 respectively). FT/E2 showed fair AUC (AUC=0.727). Serum FT showed good AUC (AUC=0.882), TT, Combined T/E2 and FT, Combined TT and E2 showed excellent AUC (AUC=0.900, 0.903, 0.958 respectively). 5. Using regression analysis for prediction of sexual desire in old men, using age, and prolactin, SHBG, TT, E2, TT/E2 and FT as covariates, the results showed that lower levels of serum prolactin and SBHG as well as higher levels of serum TT, E2, TT/E2 and FT were associated with higher sexual desire in unadjusted model. However, after adjustment of other co-variants , the results revealed that only lower SBHG levels, higher TT and FT were the only predictors for higher sexual desire. 6. Regression analysis for prediction of SDI-2 within old men, using age, and prolactin, SHBG, TT, E2, TT/E2 and FT as covariates. Lower prolactin, SBHG levels, higher TT, E2, TT/E2 and FT were associated with higher SDI-2 in unadjusted model. However, after adjustment by significant covariates in unadjusted model, revealed that only lower SBHG levels, higher TT and FT were the only predictors for higher SDI-2. 7. Many covariates studied for discrimination between normal and low sexual desire in old men groups, showed that the best of them were TT+E2+FT , TT+FT , TT/E2+prolactine, TT/E2+SHBG, TT+E2, Age+TT, TT alone. Followed by FT2 alone, FT+E2, Age+FT. Conclusions : - Older men with low sexual desire had significantly lower total and free testosterone. - There are significant positive correlations between FT and FT/E2 ratio and both sexual desire score of IIEF and SDI-2 suggesting a role for FT/E2 balance in sexual desire function in old men. - True androgen deficiency (FT) and true T/E2 imbalance (FT/E2 ratio) may have a role in discrimination between low and normal sexual desire in older men. - The best predictors for low sexual desire in older men were age+TT, TT alone, FT alone, TT+E2, age+E2. - However, our study failed to show significant correlations between total T, E2 or TT/E2 ratio and sexual desire score of IIEF and SDI-2.