animals. Fluoxetine, which inhibits serotonin uptake and therefore keeps serotonin levels high, seems to be related to increased levels of prolactin, a hormone that is known to reduce testosterone levels. 30 Another study shows that large intravenous doses of the amino acid tryptophan, a precursor of serotonin, will increase prolactin levels. 31 These studies suggest to researchers that high serotonin levels may reduce testosterone, at least slightly, by raising prolactin levels.
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Anyone with a friend who's been successfully treated with Prozac knows how elevated levels of serotonin affect personality. People who take Prozac are likely to be calmer, more confident, less irritable, more optimistic, less impulsive, and more pleasant to be around than they were before they started taking the drug. In some species of monkeys, alpha males are likely to be high in serotonin. As described in Chapter 5, female vervet monkeys like high-serotonin males and help them gain leadership roles. Such high-serotonin males are dominant, as high-testosterone males are, but they are calmer. Apparently the females appreciate the calmer and less violent leadership style of high-serotonin males. As far as peaceful behavior goes, the worst combination would seem to be low serotonin together with high testosterone. A person with this kind of mix would likely be both impulsive and dominant. 32
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Sometimes when we examine self-confident, dominant men, expecting them to be high in testosterone, we find they are not. For example, we studied an outdoorsman who lived in Alaska and spent weeks alone in the wilderness. He had a touch of vanity, and he always came back to civilization looking neat, with his beard and mustache in good shape. Suzanne Womack, who was a friend of his, said he had panache and sex appeal, and she thought he would be high in testosterone. We checked him out (after she collected saliva from him on a trip to Alaska) and found that his testosterone level was average. I suspect, but do not know, that his serotonin level was high. He had the kind of calm competence associated with leadership, the kind that makes high-serotonin male vervet monkeys attractive to females. 33 Two other people Suzanne checked out from Alaska were mountain climbers, both very high in testosterone. In exploring other characteristics with these men, she asked one to describe how high his sex drive was. He said, "Ballistic!"
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We did not assay the mountain climber's other hormone levels, but
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