Hypogonadal men and erections

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COMMENTS: The following is from a discussion on a private sexology list serve.The writer is a professor of reproductive biology.

There are at least two studies that found that hypogonadal men get erections as readily as do men with male-typical T levels when exposed to sexual stimuli. T administration didn't increase erections. The only difference between hypogonadal men and controls was that the hypogonadal men maintained their erections for longer than did the controls. However, the HG men had to be exposed to sexual stimuli to get erections.

The big difference between hypogonadal men and controls was that HG men don't show spontaneous erections and don't have nocturnal erections.

Thus without T the motivation for an erection is missing, but men are capable of having erections when exposed to erotic stimuli.

Here are two reference for human studies:

Bagatell has shown that suppressing male T with a GnRH analogue markedly reduces male sexual desire, and masturbation frequency. The effects of T in men on modulating motivation are clear.  There does not appear to be any androgen influence on the males capacity to get an erection in response to sexual stimulation.  By the way, we found the same thing in monkeys whose androgens were suppressed with a GnRH analogue. Motivation to mate was reduced. If the male was high-ranking he continued to mate (female monkeys initiate sex in our groups so sex didn't depend on the male's motivation), but low ranking males stopped altogether reflecting that they needed the motivation to mate to overcome the male-male competition in the group.  Phoenix reported years ago that male monkeys who had been castrated for more than 5 years still got erections in response to being with a receptive female and about 25% of them continued to mate and show ejaculatory reflexes.

Here's the Bagatell reference.1994. Effects of endogenous testosterone and estradiol on sexual behavior in normal young men.

And our monkey reference  1991. Antide (Nal-Lys GnRH antagonist) suppression of pituitary-testicular function and sexual behavior in group-living rhesus monkeys.