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Hormones and Personality, Part 1: Sex and Gender
by Dario Nardi, Ph.D.

Understanding hormones helps us decipher the relationship between personality and gender. “Gender” is cultural while “sex” is biological. We often associate hormones with adolescence, midlife and monthly cycles. However, the greatest influence on sex is in the womb as the brain and body of the fetal boy or girl is developing. There are over eighty known hormones. Almost all influence personality in some way and at least nine vary greatly with gender. In many cases, the relationship between hormones and personality is a two-way street. First, personality influences how we respond to our genetic heritage; and second, our hormones influence personality expression. This month we focus on four noteworthy hormones – testosterone and estrogen, vasopressin and oxytocin – plus briefly touch on five other hormones related to sex and gender including progesterone, DHT and Vasotocin.

Testosterone (and DHT)
Men produce ten times more testosterone than women, so even low testosterone men have more than any woman. Physically, it generates male traits such as body hair and baldness, and promotes libido, sperm production and potency, male musculature and deeper voice. Psychologically, testosterone promotes:

  • a sense of separateness
  • aggression and risk-taking
  • sex drive (but not touch affection) and sexual fantasy
  • anxiety or energy leading to poor concentration
  • assertiveness and self-confidence
  • visual-spatial ability and interest in moving things
  • violent, criminal, or psychotic behavior

In men, testosterone rises and falls in response to winning or losing one’s place in the social order, such as losing a game or gaining a promotion. It is higher for men in high-powered leadership positions. Particularly in early childhood, boys prefer focusing their attention on toys and other objects that can move and that they can move around.

Women have some testosterone, produced by their adrenal glands. In women, testosterone is higher in careerists compared to at-home mothers, and women's visual test scores increase when given testosterone. It also promotes sex drive for women.

DHT, or di-hydro-testosterone, is a strong form of testosterone. In the male fetus, DHT helps develop the prostate gland and scrotum. In adult men, high levels may lead to prostate problems, and to male pattern baldness. Drugs that halt or reverse baldness block the conversion of testosterone to DHT. Overall, the more DHT the more the physical sex characteristics a male has.

Beginning in midlife, a man’s testosterone drops and the small amount of estrogen produced by his adrenal glands inhibits aggressive behavior. Incidentally, the adrenal glands also produce hormones like adrenaline that promote strength, endurance and fight-or-flight behavior. Adrenal output is three times higher in men.

Estrogen (and Progesterone and Prolactin)
Estrogen is a female hormone that cycles monthly. Women have much more than men, so even low estrogen women have more than any man. Physically, estrogen generates female traits such as breasts and larger hips. Natural estrogen prevents many degenerative diseases. When it peaks, estrogen improves sleep, skin, odor, memory, and sensory acuity. Psychologically, estrogen promotes:

  • a stable mood and a sense of well-being
  • feminine sexual behavior
  • neuron growth and improved cognition

Women also produce progesterone, which monthly prepares the body for pregnancy and counters estrogen’s effects. It causes PMS. If estrogen’s role is to attract a mate then progesterone’s role is to repel dangers to pregnancy and offspring. In women after menopause, estrogen drops and trace testosterone promotes more “masculine” behaviors. In men, some estrogen is necessary to maintain strong bones. Caretaking males show higher estrogen.

Another important "female" hormone is prolactin. Prolactin is produced by the pituitary and the uterus. Like all hormones, prolactin is present in men and woman. However, women have far more. It develops a woman’s breasts at puberty by activating mammary gland cells, and it stimulates milk production in nursing mothers. It also inhibits sexual desire and reduces the chance of pregnancy (while the mother is nursing her baby). High prolactin inhibits testosterone, depresses sensation and alertness, and promotes mild inertia and fatigue. This mild inertia has been described as a non-anxious meditative state conducive to nesting behavior. Research suggests that women who suffered from abusive, absent or alcoholic fathers have higher prolactin levels. Prolactin also rises during winter months. Low prolactin causes restlessness and lack of interest in nesting behaviors.

Humans are "naturally female." Testosterone and related hormones masculinize boys in the womb, "lateralizing" the male brain into specialized compartments. In contrast, estrogen promotes neuron interconnections for a more distributed female brain. This effect is strongest in children but even late in life women recover faster from strokes because of this. Related to personality, research suggests women make use of all mental functions more equally while men make heavier use of particular mental functions.

Vasopressin (and Vasotocin)
Vasopressin is made in the brain. Both men and women make it. However, the male hormone testosterone synergizes with vasopressin – the two greatly enhance each other. A woman and man might have equal levels of vasopressin but the man experiences stronger effects. Physically, vasopressin causes water retention and high blood pressure; high levels may increase forehead size. Personality wise, vasopressin influences male social and sexual behavior, public communication, and paternal behavior. In animals (mammals), it promotes aggression, territorial competition and dominance with other males. It bonds males to mates and children. For men, it also promotes partner recognition, sexual arousal, courtship behavior, monogamy, pair bonding and mate guarding. Vasopressin also improves cognitive ability by enhancing memory. It allows one to feel separate, with dampened emotional responses and more "sensible" or "reasonable" behavior. Depressed people also have higher vasopressin.

Vasotocin is a variation of vasopressin found in fish, birds and frogs. It promotes vocalization, singing, mating calls and territorial behavior. It causes male animals to respond to the sight of attractive females. It is found in the human visual system (pineal gland), and male human bonding tends to be more visual. This might explain why adolescent boys of all types are often preoccupied with images of beautiful potential mates!

Oxytocin (and Isotocin)
Oxytocin is made in the brain. Both women and men make it. However, the female hormone estrogen synergizes with oxytocin – the two greatly enhance each other. A man and women might have equal levels of oxytocin but the woman experiences stronger effects. Physically, oxytocin facilitates childbirth and nursing for women. In both sexes, it increases by five-fold during sex. In men, however, it immediately drops and vasopressin rises sharply right afterward - explaining why men generally feel a sudden sense of separateness! Personality wise, oxytocin promotes touching, affection and bonding. In both men and women it rises instantly with a single touch. Oxytocin also influences female social behavior. It promotes "nesting"; monogamy and pair bonding; the nurturing, acceptance and protection of offspring; and pup-retrieval in animals. It influences mate selection. Many of these effects are confirmed in humans as well as animals. For all its positive benefits, high oxytocin inhibits cognitive ability by impairing learning and memory. It encourages emotional extremes but it also prevents depression.

Isotocin is a form of oxytocin found in non-mammals. It causes females to respond to male mating song. Its presence in humans is un-investigated. However, human female bonding tends to be more auditory than visual. This might explain why adolescent girls of all types often greatly enjoy a crooning singer’s voice.

Hormones, Sex and Personality
There are several working hypotheses about hormones and personality. One hypothesis is that personality is purely biological – hormones cause neurological and chemical changes that drive personality. For example, the descriptions of vasopressin and oxytocin parallel two mental functions desribed by Carl Jung - Thinking and Feeling. However, the picture is clearly more interesting that this! Consider two males with very different personalities. Both these males could easily both have strong visual skills, albeit in different areas, even though visual skill is hormone-related. So right away we see hormones can't "cause" personality or even correlate one-to-one. A second hypothesis is that biology only influences personality – our biology poses various developmental challenges, influences how we develop and may explain the origin of social stereotypes. Consider oxytocin from this perspective. A woman who prefers Thinking would take practical logical steps to organize and protect her family, while a woman who prefers Feeling would work from strong values and beliefs about her family. Personality would influence how each woman consciously deals with the same physiological drives and characteristics. Right now we don’t know the whole story.

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