hormones

‘Get ready, little lady. Hell is coming to breakfast.’ –The Outlaw Josey Wales (1976)

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Two studies done at the University of Minnesota Medical School and published in the early 1980’s measured the intensity, frequency, and durations of pelvic muscle contractions (measured with a pressure sensitive anal probe) of males and females during masturbation. There was basically no difference in the pattern of these contractions between males and females. […] A study done at Stanford University in 1994 found no significant gender differences in observed increases in heart rate, blood pressure, oxytocin, and anal contractions during orgasm.

{ Psychology Today | Continue reading }

The refractory period is the recovery phase after orgasm during which it is physiologically impossible for a man to have additional orgasms. This phase begins immediately after ejaculation. […] Although it is generally reported that women do not experience a refractory period and can thus experience an additional orgasm (or multiple orgasms) soon after the first one, some sources state that […] women may also experience a moment after orgasm in which further sexual stimulation does not produce excitement. […] clitoral hypersensitivity after orgasm can effectively create a refractory period. these women may be capable of further orgasms, but the pain involved in getting there makes the prospect undesirable. […]

the refractory period varies widely among individuals, ranging from minutes to days […] According to some studies, 18-year-old males have a refractory period of about 15 minutes, while those in their 70s take about 20 hours, with the average for all men being about half an hour. Although rarer, some males exhibit no refractory period or a refractory period lasting less than 10 seconds. […]

An increased infusion of the hormone oxytocin during ejaculation is believed to be chiefly responsible for the male refractory period, and the amount by which oxytocin is increased may affect the length of each refractory period. Another chemical which is considered to be responsible for the male refractory period is prolactin, which is repressed by dopamine, and is responsible for sexual arousal. […]

One alternative theory explains the male refractory period in terms of a peripheral autonomic feedback mechanism, rather than through central chemicals like oxytocin, serotonin, and prolactin. Autonomic feedback is already known to regulate other physiologic systems, such as breathing, blood pressure, and gut motility. This theory suggests that after male ejaculation, decreased wall tension in structures such as the seminal vesicles leads to a change in the fine autonomic signals sent from these organs, effectively creating a negative feedback loop. Such a mechanism is similar to decreased gastric and bowel motility once gastric contents have passed through. Once the feedback loop has been created, the refractory period remains until the loop is broken through restoration of the wall tension in the seminal vesicles. As men age, the time to restore tension in the seminal vesicles increases.

{ Wikipedia | Continue reading }

You run into an asshole in the morning, you ran into an asshole. You run into assholes all day, you’re the asshole.

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During my clinical internship over 20 years ago, my boss, a psychiatrist, asked me to research how PMS prevents women from thinking clearly. I told him he was a relic of the Stone Age. Women were as consistently clearheaded as men, if not more so.

But recently, a researcher in my lab, Joe Andreano, an expert on female hormones, showed me some surprising data. As a woman’s levels of progesterone and estrogen vary, so does the connectivity between two brain networks: the default mode network and the salience network. These networks play key roles in creating your emotional life.

If I hadn’t seen the data with my own eyes, I wouldn’t have believed it.

When scientists say that brain networks are “strongly connected” or have “increased connectivity,” it means that the neurons have an easier time passing information back and forth. In the case of the default mode and salience networks, increased connectivity means (among other things) that you may experience more powerful negative emotions. In earlier research, for example, my colleagues and I found that people reported more intense sadness when watching the sentimental movie “Stepmom” and more intense fear when watching the horror movie “The Ring Two” in the moments when these brain networks were more connected.

There has also been a flurry of recent studies indicating that certain cocktails of ovarian hormones can make women feel lousy, particularly a week or so before menstruation. Female test subjects who receive ovarian hormones designed to mimic the menstrual cycle, for example, report an increase in negative mood. They also remember negative material better, and they show enhanced stress responses. […]

 I’m not saying that women turn into helpless snowflakes for a few days each month. I’m just saying that the biology is real: Some women may have a short window before their period when, if something bad happens, they will feel more negative or stressed and will remember that unpleasant event more easily.

A few bad feelings or memories aren’t inherently harmful, of course. But this window of vulnerability, combined with other risk factors, could increase the odds of developing mood disorders like depression.

{ NY Times | Continue reading }

enamel on linen { Christopher Wool, Untitled, 1998 }

Ho hang! Hang ho! And the clash of our cries till we spring to be free.

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Why the Victorian era saw a surge in female births and war begets boys

There is empirical evidence that heavy sexual activity increases the chances that conception will occur before the most fertile time of the female cycle, as the woman may be pregnant by then. And the data also suggest that, possibly for hormonal reasons, such conceptions are slightly more likely to be boys. “It doesn’t take much imagination to suppose that the ends of wars, with servicemen home on leave or returning home, are associated with fairly intense sex – more babies were born in the UK in 1919 than any other year in history. Put all these together and you get the conclusion – frantic fornication breeds boys.”

[…]

Which brings us back to the mysterious surge of female births in the late Victorian period. Could it be that, in the same vein in which heavy sexual activity increases the sex ratio, a  trend towards sexual inactivity lowers it? “Victorian morality” distinguished itself through a set of values that espoused sexual restraint, with an increased condemnation of masturbation and sexual activity in general, repressing any form of sexuality other than penetrative intercourse. And indeed, statistics reflect a steady decline of sexual activity throughout the Victorian period, reaching its lowest point in the year 1898. But as there was less sex going on, conception tended to occur around the most fertile time of the months, bestowing a (relative) excess of baby girls on the Victorians.

{ Rolf Degen | Continue reading }

Hypothesis 1

Up to circa two decades age, it was generally supposed – but without hard supporting evidence – that pregnant women exposed to adverse environmental circumstances were at increased risk of foetal loss, and that male foetuses were at greater risk than female foetuses; and that therefore the liveborn infants produced by stressed women contained a higher proportion of daughters. That hard evidence has now been accumulated in a series of papers by Catalano and colleagues, and others.

Using time-series analysis, it has been shown that the Sex ratios at birth (SRB) briefly declined, slightly but significantly, some three to five months after many catastrophic and other adverse events e.g. the terrorist attacks on September 11th, 2001; the Troubles in Northern Ireland (1969–1998), the Breivik shooting in 2011 in Norway, the Sandy Hook shooting in 2012 in Connecticut; the assassination of President Kennedy [though the effect in this case was more marked in non-White than White births]. […]

Thus there is overwhelming evidence that sex ratios at birth are partially controlled by maternal stress-induced selective culling of frail males in utero, resulting in a conception cohort with a low sex ratio at birth. It has also been postulated that the ratio may be skewed because of fertilization of non-optimally matured oocytes under these circumstances. Moreover, it has also been hypothesized that higher coital rates will lead to ejaculation of newly formed spermatozoa cells, possibly leading to a preponderance of Y-sperm since it is also hypothesized that X-sperm age faster and are eliminated earlier.

However, it will be appreciated that selective culling of frail males during pregnancy cannot explain some of the established variations of SRB. First, it cannot explain why some reported sex ratios are higher than prevailing norms. Second, it cannot explain why these norms almost always exceed 0.5 (equal numbers of males and females).

Hypothesis 2

It has been hypothesized that human sex ratios at birth are partially controlled by the parental hormone levels of both parents around the time of conception. Ex hypothesi, high levels of testosterone (in either parent) and/or of oestrogen (in the mother), are associated with subsequent male births. And high levels of gonadotrophins (in either parent) are associated with subsequent female births. Most of this evidence is observational and correlational, and is in accordance with the hypothesis of Trivers & Willard.

{ Early Human Development | Continue reading }

lithograph { Ellsworth Kelly, Small Blue Curve, 2013 }

See problems as challenges, not threats

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Because ovulating (i.e., high-fertility) women are both more attractive to men and also more attracted to (desirable) men, ovulating women may be perceived to pose heightened threats to other women’s romantic relationships. Across 4 experiments, partnered women were exposed to photographs of other women taken during either their ovulatory or nonovulatory menstrual-cycle phases, and consistently reported intentions to socially avoid ovulating (but not nonovulating) women - but only when their own partners were highly desirable. Exposure to ovulating women also increased women’s sexual desires for their (highly desirable) partners. These findings suggest that women can be sensitive to subtle cues of other women’s fertility and respond (e.g., via social exclusion, enhanced sexual attention to own mate) in ways that may facilitate their mate retention goals while not thwarting their affiliative goals.

{ Journal of Personality and Social Psychology | Continue reading }

Using luteinizing hormone tests to verify ovulation, across two studies (Samples 1 and 2), we found that women whose partners were relatively low in sexual desirability felt less close to their partner (Samples 1 and 2) and were more critical of their partner’s faults (Sample 2) on high-fertility days of the cycle just prior to ovulation compared with low-fertility days of the cycle. Women whose partners were relatively high in sexual desirability felt closer to their partner (Sample 1) and more satisfied with their relationship (Sample 2) on high- than low-fertility days of the cycle. There were no such shifts in women’s commitment to their relationship. Therefore, partner sexual desirability predicts women’s high-fertility assessments of relationship quality but not their intentions to stay in their relationship, consistent with the dual mating hypothesis. These findings suggest that variations across the ovulation cycle in women’s reproductive hormones play an important role in relationship dynamics.

{ Hormones and Behavior | PDF }

images { 1. Frederike Helwig | 2. Bonnie and Clyde (1967), publicity still, Faye Dunaway }

rave in2 the joy fantastic

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Research has found that estradiol positively and progesterone negatively predicts women’s sexual desire. […]

The current study extended these findings by examining, within a sample of 33 naturally cycling women involved in romantic relationships, hormonal correlates of sexual attraction to or interests in specific targets: women’s own primary partner [in-pair] or men other than women’s primary partner [extra-pair]. […]

Whereas estradiol levels were associated with relatively greater extra-pair sexual interests than in-pair sexual interests, progesterone levels were associated with relatively greater in-pair sexual interests.

{ Hormones and Behavior | Continue reading }

photo { Maxime Ballesteros }

‘bathe in bat your eyelashes with dermatologist recommended water’ —@lady_products

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Research has shown that humans consciously use alcohol to encourage sexual activity. […]

In the current study, we examined if males exposed without their knowledge to pheromones emitted by fertile females would increase their alcohol consumption, presumably via neurobehavioral information pathways that link alcohol to sex and mating. We found that men who smelled a T-shirt worn by a fertile female drank significantly more (nonalcoholic) beer, and exhibited significantly greater approach behavior toward female cues, than those who smelled a T-shirt worn by a nonfertile female.

{ Experimental and Clinical Psychopharmacology | Continue reading }

photo { Miss August, 1957 }

Now, baby, Cissy Caffrey said. Say out big, big. I want a drink of water. And baby prattled after her: A jink a jink a jawbo.

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Recent studies have shown that women are more sensitive than men to subtle cuteness differences in infant faces. It has been suggested that raised levels in estradiol and progesterone may be responsible for this advantage. […]

Thirty-six women were tested once during ovulation and once during the luteal phase of their menstrual cycle. In a two alternative forced-choice experiment, participants chose the baby which they thought was cuter (Task 1), younger (Task 2), or the baby that they would prefer to babysit (Task 3). […]

During ovulation, women were more likely to choose the cuter baby than during the luteal phase, in all three tasks. These results suggest that cuteness discrimination may be driven by cyclic hormonal shifts.

{ Hormones and Behavior | Continue reading }

art { Henri Chopin, La crevette amoureuse, 1967-1975 }

Your reputation precedes you

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The idea of two sexes is simplistic. Biologists now think there is a wider spectrum than that.

The presence or absence of a Y chromosome is what counts: with it, you are male, and without it, you are female. But doctors have long known that some people straddle the boundary — their sex chromosomes say one thing, but their gonads (ovaries or testes) or sexual anatomy say another. Parents of children with these kinds of conditions — known as intersex conditions, or differences or disorders of sex development (DSDs) — often face difficult decisions about whether to bring up their child as a boy or a girl. Some researchers now say that as many as 1 person in 100 has some form of DSD. […]

That the two sexes are physically different is obvious, but at the start of life, it is not. Five weeks into development, a human embryo has the potential to form both male and female anatomy. Next to the developing kidneys, two bulges known as the gonadal ridges emerge alongside two pairs of ducts, one of which can form the uterus and Fallopian tubes, and the other the male internal genital plumbing: the epididymes, vas deferentia and seminal vesicles. At six weeks, the gonad switches on the developmental pathway to become an ovary or a testis. If a testis develops, it secretes testosterone, which supports the development of the male ducts. It also makes other hormones that force the presumptive uterus and Fallopian tubes to shrink away. If the gonad becomes an ovary, it makes oestrogen, and the lack of testosterone causes the male plumbing to wither. The sex hormones also dictate the development of the external genitalia, and they come into play once more at puberty, triggering the development of secondary sexual characteristics such as breasts or facial hair. […]

For many years, scientists believed that female development was the default programme, and that male development was actively switched on by the presence of a particular gene on the Y chromosome. In 1990, researchers made headlines when they uncovered the identity of this gene, which they called SRY. Just by itself, this gene can switch the gonad from ovarian to testicular development. For example, XX individuals who carry a fragment of the Y chromosome that contains SRY develop as males.

{ Nature | Continue reading }

49 days, surely I should be feeling a whole lot better

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Does morality depend on the time of the day? The study “The Morning Morality Effect: The Influence of Time of Day on Unethical Behavior” published in October of 2013 by Maryam Kouchaki and Isaac Smith suggested that people are more honest in the mornings, and that their ability to resist the temptation of lying and cheating wears off as the day progresses. […]

One question not addressed by Kouchaki and Smith was whether the propensity to become dishonest in the afternoons or evenings could be generalized to all subjects or whether the internal time in the subjects was also a factor.

All humans have an internal body clock — the circadian clock — which runs with a period of approximately 24 hours. The circadian clock controls a wide variety of physical and mental functions such as our body temperature, the release of hormones or our levels of alertness. The internal clock can vary between individuals, but external cues such as sunlight or the social constraints of our society force our internal clocks to be synchronized to a pre-defined external time which may be quite distinct from what our internal clock would choose if it were to “run free”. Free-running internal clocks of individuals can differ in terms of their period (for example 23.5 hours versus 24.4 hours) as well as the phases of when individuals would preferably engage in certain behaviors. […]

Some people like to go to bed early, wake up at 5 am or 6 am on their own even without an alarm clock and they experience peak levels of alertness and energy before noon. In contrast to such “larks”, there are “owls” among us who prefer to go to bed late at night, wake up at 11 am, experience their peak energy levels and alertness in the evening hours and like to stay up way past midnight. […]

The researchers Brian Gunia, Christopher Barnes and Sunita Sah therefore decided to replicate the Kouchaki and Smith study with one major modification: They not only assessed the propensity to cheat at different times of the day, they also measured the chronotypes of the study participants. Their recent paper “”The Morality of Larks and Owls: Unethical Behavior Depends on Chronotype as Well as Time of Day” confirms that Kouchaki and Smith findings that the time of the day influences honesty, but the observed effects differ among chronotypes. […]

[M]orning morality effect and the idea of “moral exhaustion” towards the end of the day cannot be generalized to all. In fact, evening people (”owls”) are more honest in the evenings. […]

Gunia and colleagues only included morning and evening people in their analysis and excluded the participants who reported an intermediate chronotype, i.e. not quite early morning “larks” and not true “owls”. This is a valid criticism because newer research on chronotypes has shown that there is a Gaussian distribution of chronotypes. Few of us are extreme larks or extreme owls, most of us lie on a continuum.

{ Fragments of Truth | Continue reading }

photo { Steven Meisel }

I eat cannibals

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Campion was an ophthalmologist […] He became a testosterone doctor. […] The initial session costs $5,000, and the monthly charges are over $1,000. Clients get their blood work done every three months, so that Campion can keep tabs on how their “hormonal balancing” is going. Most patients lock into a permanent testosterone regimen, as Campion has. “I will take testosterone for the rest of my life,” he says. […]

Testosterone can be manufactured cheaply in large quantities, and the risks seem manageable for most people. Users report increased energy, more muscle mass, decreased body fat, greater sex drive, and a general sense of well-being. In short, it’s one of the most transformative substances a human can take. […]

According to a study by University of Texas epidemiologist Jacques Baillargeon, nearly four percent of men in their 60s are taking testosterone. The number of men between 40 and 64 went up 77 percent from 2010 to 2013 to 1.5 million men.

{ Fusion | Continue reading }

art { Andy Warhol, Eight Elvises, 1963 | The current owner and location of the painting, which has not been seen publicly since the 1960s, are unknown }

Baby baby baby, look to the sky, seeking to find, the third eye

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Impending fatherhood can lower two hormones–testosterone and estradiol–for men, even before their babies are born, a new University of Michigan study found.

Other studies indicate that men’s hormones change once they become fathers, and there is some evidence that this is a function of a decline after the child’s birth. […]

Expectant mothers experience significant hormone changes throughout the transition to parenthood, but less has been known about the prenatal hormone changes among soon-to-be fathers.

Women showed large prenatal increases in all four hormones, while men saw declines in testosterone (which is associated with aggression and parental care) and estradiol (which is associated with caregiving and bonding). No changes were found in men’s cortisol (a stress hormone) or progesterone (which is associated with social closeness and maternal behavior).

{ EurekAlert | Continue reading }

sculpture { Duane Hanson, Old Man Playing Solitaire, 1973 }

‘Let’s break shit.’ –Guy Vidra

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The Male Idiotic Theory (MIT) stipulates that the reason men are more prone to injury and death is simply because they “are idiots and idiots do stupid things“. Despite tons of anecdotal evidence confirming MIT, there’s never been a systematic analysis on sex differences in idiotic risk taking behaviour. Until now.

In a new study published in BMJ, researchers obtained 20 years worth of data from the Darwin Awards to tally up the sex of each year’s winner. For those not in the know, the Darwin Awards are given to people who die in such astonishingly stupid ways that “their action ensures the long-term survival of the species, by selectively allowing one less idiot to survive”. […]

Men made up a staggering 88.7 % of Darwin Award winners in 318 examined cases.

{ Neurorexia | Continue reading }

related { Males are more likely to die than females while in the womb }