The secret forces that are making you stressed, hungry and sexy

Hormones get no respect.

We think of them as the elusive chemicals that make us a bit moody, but these magical little molecules do so much more.

“Hormones control growth, metabolism, behavior, sleep, lactation, stress, mood swings, sleep-wake cycles, the immune system, mating, fighting, fleeing, puberty, parenting and sex,” writes Columbia professor Dr. Randi Epstein in “Aroused: The History of Hormones and How They Control Just About Everything” (W. W. Norton & Company), out now.

Since the term “hormonal” hit the medical lexicon in the early 1900s — and we began studying them in earnest in the 1920s — these “loopy chains of amino acids or rings of carbon atoms” have long fascinated, excited and controlled us.

The more we learn, the more we realize that they are, as Epstein writes, “The chemistry of being human.”

Here are just a few examples from Epstein’s book of how these miraculous tiny power players run the show:

You can also blame leptin for those pesky 15 pounds you just can’t lose no matter what. “Most people tend to have a weight that is ‘normal,’ or feels right for them, even though it may not be a fashionable rail-thin physique. When we eat less and shrink our fat stores, leptin dips too, prompting cravings to eat our way back to our curvier starting point,” writes Epstein. “The good news is that it works both ways. Sustainable weight loss is possible with slow, gradual diets that adjust the set point, perhaps by resetting leptin levels.”Epstein calls leptin “the hormone equivalent of an alarm system” — if an alarm system can make you endlessly hungry. We’ve called it the “obesity hormone” or the “fat hormone” — and with good reason. The protein released by the hypothalamus is made up of fat cells that travel to the brain and alert the body when energy resources are low. When you don’t eat, leptin drops and interferes with other hormones released by the hypothalamus, thoroughly screwing up your system. That’s why women who starve themselves stop menstruating and become infertile. “Doctors have known about these dangers for years” especially in people who suffer from anorexia “but only recently has leptin been identified as the linchpin that triggers the turmoil,” writes Epstein.

Sadly, leptin injections or replacement therapies to combat overeating have remained a pipe dream. The only people who seem to respond are people born without the leptin hormone. The rest of us must continue to struggle against these hangry little chemicals.

Found above the kidneys, the adrenal gland helps manage the “fight or flight” response in stressful situations thanks to the release of hormones adrenaline and noradrenaline into the bloodstream. The “stress hormones,” as they’re called, do a number on the body, causing the pupils to dilate, the face to either flush or lose its color, the muscles to tense up, our skin to get goose bumps, and our immune and digestive systems to shut down. Humans aren’t alone in this reaction. Animals experience the fight-or-flight response, too, but a 2018 study out of Korea published in PLOS Genetics theorizes that humans and chimpanzees have more robust fight-or-flight responses because our species has had constant threats of warfare and evolutionarily benefited from battle-ready bodies. Trouble is, this fear response not only adds stress to the heart and lungs, it also can mess with our skin and cause us to age faster — actually breaking us down quicker on a cellular level.

The testicles are located outside of the body where the sun doesn’t shine and they’re responsible for releasing testosterone. Testosterone aids in the growth of facial hair, deepening of voice and growth in boys when they hit puberty. (Ovaries and adrenal glands also produce testosterone at lower levels in girls and women.) Fun fact: The testes are about two degrees cooler than the rest of the body, as lower temps are better for sperm production.

We’ve tried a lot of strange experiments with those dangly doodads. The first ever experiment with hormones happened in 1848 when German researcher Arnold Berthold testicle-swapped his roosters — reinserting some on bellies or taking a testicle from one rooster and implanting it into another one. He found that no matter where you put the testicles, there was an effect: Those without testes got fat, lazy and less interested in sex, while those who were packing tummy testes saw the opposite effect.

Other (similarly bizarre) experiments followed. In one, the researcher removed male rat testicles and watched the rats “wither.” Then he inserted the testicles into the rats’ bellies and voila! The rats’ energy increased and their sex drive surged, writes Epstein. The researcher also removed ovaries from female rats and attached testicles to their bellies and found that the rats had grown “a large clitoris, coarse hair and behave[d] exactly like a normal male,” Epstein writes.

Over a man’s life, there is a considerable drop in the production of testosterone. Starting at age 30, a man’s testosterone drops by 1 percent a year. “It’s a slow leak, like a tiny hole in a bike tire that may not be noticeable until the tire is nearly flat.” This may explain young men’s obsession with Air Jordans and other “cool” clothing brands. According to a 2018 study by Nature magazine, giving men more testosterone makes them prefer high-status items.

This almond-sized gland in the forebrain controls the autonomic nervous system — breathing, digestion and heartbeat — and aids in everything from body temperature to hunger to sleep.

The hypothalamus also plays a role in a woman’s least favorite rite of passage: menopausal hot flashes. Eighty percent of women who reach their 50s will experience them.
Studies have shown that the neurons within the hypothalamus actually change as we age — one study shows neurons the size of plump blueberries in postmenopausal women, while the same neurons are the size of small capers in premenopausal women.

UIG via Getty Images

This shows how “in menopause, the brain gets the signal that estrogen is low and fires up cells that should lead to an estrogen boost,” writes Epstein. “But because the ovaries are no longer functioning, the estrogen level doesn’t rise. The brain keeps getting bombarded with we-need-more-estrogen messages. The continued assault pumps up the cells.”

These “pumped up” cells may interfere with older women’s internal control system, leading to those dreaded hot flashes. Drugs used to block the swelling are currently being tested and the “preliminary results are promising,” writes Epstein. Today the most effective treatment for hot flashes is hormone replacement therapy, but that comes with its own set of risks (like increased chances of certain cancers, heart attack and stroke) so hope continues for a new drug that delivers relief without these serious issues.

The pituitary gland releases oxytocin, a complex chemical that is involved in nearly every bodily function. It prompts the uterus to contract during childbirth and triggers the breast ducts to release milk. But it’s also well known as the “trust hormone” or “cuddle hormone” — because it’s the chemical that seems to bridge emotional connection between mothers and newborns, between lovers and even between dogs and their owners. A 2009 study published in the journal Hormones and Behavior showed that playing with your dog can create an oxytocin surge in both humans and canines.

But oxytocin also has a dark side, too. A 2014 study published in the Proceedings of the National Academy of Sciences in the United States of America showed that when you give the chemical to people playing a simple coin-toss game, they were more likely to cheat. In the study, researchers asked 60 volunteers to predict a coin toss. Since the researchers gave cash for wins and volunteers only had to report their results after the toss, lots of people — around 67 percent — cheated. But when they sniffed oxytocin they were even worse, cheating around 80 percent of the time. Other studies have supported the nefarious role of oxytocin, showing that it can reduce our ability to trust or cooperate and also increases the bias we feel toward “outsiders.”

The pea-sized pineal gland is shaped like a pine cone and sits deep within the brain. It produces melatonin, which helps us sleep and controls our circadian rhythm. The way this works is that our retinas communicate lightness — or, in the case of sleep, time darkness — to the hypothalamus, which then sends a message to the pineal gland, which revs up its melatonin production to get us ready for sleep. Melatonin, interestingly, does more than just help us get some shut-eye, it also plays a role in our reproduction by helping to release another hormone called the gonadotropins, which stimulates ovulation in women and sperm production in men. Doctors prescribe gonadotropin injections to people with fertility issues.

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