madman
Super Moderator
On the basis of the present knowledge, it cannot be excluded that the aging-associated high LH levels of the male may have an effect on the endothelial cells of the spongious tissue through the LHCG receptors. Furthermore, as the LH and FSH receptors belong to the same superfamily of G-coupled glycoprotein hormone receptors [1,2] with the same a subunit and 40% homology in the sequence of the ectodomains and 70% homology in the functionally significant serpentine domain of the genes of their b subunits [38] and as it is known that chorionic gonadotrophin in high concentrations can inappropriately stimulate the FSH receptor [39] and the TSH receptor [40], it is not excluded that the same may also occur vice versa, if the FSH or the TSH levels are high. The role of high FSH may be strengthened by the observations of Santi et al. [41], who reported a case of an atypical giant pituitary adenoma secreting follicle-stimulating hormone in 55-year-old patient with fatigue, loss of libido, and erectile disorder. It has also been reported that the wild-type LHCG receptors and the wild-type FSH receptors can form dimers [42], suggesting a more complex interaction between these two G-protein-coupled transmembrane receptors. However, the present results demonstrate that the high circulating LH of the aging male could possibly bind to the LHCG receptor expressed by the penile endothelial cells and perhaps induce some effects in their functions. Experimental arrangements to test this possibility should be organized in the future.
Last but not the least, it should be remembered that the postmenopausal women as well as women approaching ovulation have high serum LH levels and the pregnant women have high levels of serum hCG, suggesting that high female LH or hCG concentrations in the vaginal excretions might bind to the penile LHCG receptors, thus possibly affecting the penile endothelial cell functions. However, the LHCG receptors are expressed by cells deep inside the penile tissue, suggesting that LH or hCG in the vaginal excretions may not reach these cells without active transport at some point between the penile surface and the spongious tissue [43]. Further studies are indicated.
Last but not the least, it should be remembered that the postmenopausal women as well as women approaching ovulation have high serum LH levels and the pregnant women have high levels of serum hCG, suggesting that high female LH or hCG concentrations in the vaginal excretions might bind to the penile LHCG receptors, thus possibly affecting the penile endothelial cell functions. However, the LHCG receptors are expressed by cells deep inside the penile tissue, suggesting that LH or hCG in the vaginal excretions may not reach these cells without active transport at some point between the penile surface and the spongious tissue [43]. Further studies are indicated.
