11 Eye-Opening Facts About the Thyroid

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The human body is an amazing thing. For each one of us, it’s the most intimate object we know. And yet most of us don’t know enough about it: its features, functions, quirks, and mysteries. Our series The Body explores human anatomy, part by part. Think of it as a mini digital encyclopedia with a dose of wow.

The thyroid is a small, butterfly-shaped gland that lives just below your larynx. Its two halves, or lobes, which rest against the trachea, weigh less than an ounce. The thyroid is under the control a peanut-shaped gland in the brain called the pituitary gland, which in turn takes its commands from the hypothalamus, a region of the brain that works as the communications center for the pituitary—sending messages in the form of hormones to control the release of thyroid hormones from the pituitary.

Once stimulated, the thyroid gland takes up iodide from the foods we eat and converts it into iodine to make the thyroid hormones thyroxine (T4) and triiodothyronine (T3). These hormones are then released into the bloodstream, where they help your body regulate so many processes it would take several pages to describe them all. Generally, these hormones dictate your metabolism, digestion, fertility, weight loss, aging, and more.

Mental Floss spoke to a few experts to better understand this small but powerful gland. Here are 11 things we learned.

1. YOUR THYROID INFLUENCES EVERY CELL IN YOUR BODY.

Thyroid hormones regulate the metabolic functions of literally every cell in the body by stimulating nearly all tissues in the body to produce proteins and by increasing oxygen available to cells.

2. IT'S ALSO YOUR BODY'S FURNACE.

You can think of your thyroid gland as your body’s furnace, and your pituitary gland as its thermostat, says Michelle Corey, a functional medical practitioner and author of The Thyroid Cure: The Functional Mind-Body Approach to Reversing Your Autoimmune Condition and Reclaiming Your Health! When the furnace (thyroid) gets too cold, the thermostat (pituitary) senses it and produces TSH to stimulate thyroid hormone production, which warms you up. When the levels of thyroid hormones rise and the furnace gets too hot, the pituitary gland then slows the production of TSH, cooling you down.

3. YOUR THYROID AND YOUR LIVER HAVE A TIGHT PARTNERSHIP.

The liver is the major location where T4 is converted into the active T3. If your liver is taxed for any reason, it can’t do the job of converting these hormones, and you won’t have enough of the active thyroid hormone circulating in your body. As a result, you’ll feel sick and tired, even if you’re taking T4 hormone replacement. “If you have been diagnosed with an autoimmune thyroid condition, such as Hashimoto’s disease, supporting your liver is critical to recovery,” Corey says.

4. THYROID DISORDERS CAN BE DIFFICULT TO DIAGNOSE.

Often, symptoms of thyroid disorder may go unnoticed “since they are gradual and non-specific,” says Nilem Patel, an endocrinologist at Los Angeles’s Adventist Health White Memorial Hospital. “Left untreated, thyroid disorder can cause disruption in patients’ lives,” he says. Dysfunction in the thyroid can cause the thyroid to overproduce or underproduce thyroid hormones. If you suspect an issue with your thyroid, request tests beyond just your baseline TSH levels, including T3 and T4 levels as well as thyroid antibodies.

5. ANXIETY AND INSOMNIA CAN BE SIGNS OF AN OVERACTIVE THYROID …

Your wee hour tossing and turning, as well as a racing heart and anxiety, could actually be symptoms of hyperthyroidism, or the overproduction of thyroid hormone. Other symptoms include fatigue, weight loss, palpitations, increased heart rate, and nervousness.

6. … WHILE SUDDEN WEIGHT GAIN AND DEPRESSION MIGHT BE CAUSED BY AN UNDERACTIVE THYROID.

When these symptoms seemingly come out of nowhere, they can be evidence of an underproduction of thyroid hormone. Other common signs of a sluggish thyroid include fatigue, hair loss, constipation, dry skin, irregular menses, cold intolerance, brittle hair, slow heart rate, and general lethargy.

7. IT CAPTURES AN ESSENTIAL ELEMENT.

“The thyroid is the only gland to take up and trap iodine,” says Alan P. Farwell, section chief of endocrinology, diabetes, and nutrition at Boston Medical Center.

Thyroid hormones are also the only iodine-containing hormones. The thyroid gland not only takes up this element from dietary sources but stores a significant amount of iodinated tyrosines (a kind of amino acid) to maintain thyroid hormones in instances of iodine deficiency.

8. IT STORES A POTENTIALLY LETHAL DOSE OF HORMONES.

The gland can store a very large amount of hormone—so much that if the gland released all of its hormone into the bloodstream at once, it could kill you (this is known as thyrotoxicosis), says Linda Anegawa, a Hawaii-based physician with a specialty in obesity medicine. Fortunately thyroid hormone is very tightly regulated by constant, exquisitely sensitive signals traveling between the brain, the gland, the body’s tissues, and the blood concentrations of the hormone at any given moment.

9. THE THYROID PLAYS A CRITICAL ROLE IN PREGNANCY AND FETAL DEVELOPMENT.

To meet the increased metabolic needs of a pregnancy, a mother’s brain stimulates the thyroid gland to produce more hormone. “In the uterus, the fetal thyroid gland begins to function by 18 weeks of gestation. Should the fetus not get enough thyroid hormone from either the mother or from its own gland, severe outcomes can occur including abnormal brain development, abnormal growth of the skeletal system, problems with the placenta, or even miscarriage and increased perinatal mortality risk,” Anegawa says.

10. BALANCING YOUR THYROID MIGHT HELP YOU AVOID CHOLESTEROL-LOWERING DRUGS.

“I sometimes see patients with very elevated cholesterol on cholesterol-lowering medication that doesn’t seem to be working. But then I discover that their thyroid function is off-kilter,” says Anegawa. In these cases, she generally recommends adjusting a patient’s thyroid medicines or beginning treatment for at least six to eight weeks prior to checking the blood cholesterol level. This has helped some of her patients reduce their doses of cholesterol medicines, or stop taking them completely. “[Thyroid hormones] may someday be used as a cholesterol treatment, especially for patients who cannot tolerate statins, the most commonly used drugs,” she says.

11. SYNTHETIC THYROID HORMONE MAY HAVE EXCITING NEW MEDICAL USES.

A specially engineered form of thyroid hormone that only targets heart cells is under research as a treatment for heart failure, Anegawa says. Another form of the hormone, which selectively can enter nerve cells, may someday be a treatment for neurodegenerative disease.

10 Smart Facts About Your Gut

Colorized scanning electron micrograph of E. coli, a common gut bacteria
Colorized scanning electron micrograph of E. coli, a common gut bacteria
National Institute of Allergy and Infectious Diseases, Flickr // CC BY 2.0

Gut feelings get all the press, but your gut may be more of a thinker than you know. Some scientists now consider it a second brain. While it won’t necessarily help you study for an exam or get a promotion, your gut can influence the chemistry of your mood, emotions, immune system, and long-term health. Research even suggests the gut can “learn” new tricks through conditioning. These powerful connections are part an emerging field of science called neurogastroenterology designed to study the gut-brain link. Here are 10 facts you may not know about your gut.

1. THE GUT DOESN'T NEED THE BRAIN'S INPUT. 

You might think of your gut as a rebel against authority. It doesn’t wait for your brain’s impulses to do the important work of digestion, because it doesn’t need to—it acts as its own “brain.” No other organ, not even the all-powerful heart, can pull that off.

2. THERE ARE MORE THAN 100 MILLION BRAIN CELLS IN YOUR GUT.

Your gut’s power to think for itself is no surprise; there are millions of neurons in its lengthy coils (9 meters of intestines, from esophagus to anus). That’s more neurons than are found in the spinal cord or peripheral nervous system.

3. YOUR GUT HAS ITS OWN NERVOUS SYSTEM.

The enteric nervous system—the controlling mechanism of digestion and elimination—is the overlord of your gut, and functions all on its own. Some scientists see it as part of the central nervous system, while others consider it its own entity. It likely evolved to give the gut the go-ahead when the “got to go” impulse strikes, without requiring the brain’s sign-off, particularly when you consider the helplessness of an infant with its brand-new brain.

4. THERE'S AN INFORMATION HIGHWAY FROM YOUR GUT TO YOUR BRAIN.

There’s one big visceral nerve embedded in your gut—the vagus nerve. Research has revealed that up to 90 percent of its fibers carry information from the gut to the brain, rather than the other way around. In other words, the brain interprets gut signals as emotions. So you really should trust your gut.

5. MOST OF YOUR SEROTONIN IS IN YOUR GUT.

Some 95 percent of your body’s serotonin, that marvelous mood molecule that antidepressant drugs like Prozac keep in your body, can be found in the gut. So, it’s no wonder that diet, medications, and antibiotics can wreak havoc on one’s mood.

6. A HEALTHY GUT MAY PROTECT YOUR BONES.

In a study of the serotonin-gut relationship, scientists discovered an unexpected link between the gut and the bones. Inhibiting the gut’s release of serotonin counteracted the bone-density reduction of osteoporosis in mice. This research is going into studies on new osteoporosis-fighting drugs.

7. RESEARCH SHOWS LINKS BETWEEN AUTISM AND HAVING FEWER STRAINS OF GUT BACTERIA. 

In as many as nine out of 10 cases, autistic people have common gut imbalances such as leaky gut syndrome, irritable bowel syndrome, and fewer strains of “good” bacteria. Research on mice is looking at possible treatments of some of the behavioral disorders of autism by balancing microbes in the guts, though many warn that such treatments can’t produce a “cure” for autism.

8. FOOD REALLY DOES AFFECT YOUR MOOD. 

Different foods, when introduced to the gut via feeding tubes, have been shown to change a person's moods without the person’s awareness of what they were "eating." Fat, for instance, increased feelings of happiness and pleasure (no surprise there) because appeared to trigger the release of dopamine—the brain’s natural opiate. Carbohydrate consumption stimulated the release of serotonin, the “feel good” neurotransmitter.

9. YOUR GUT IS YOUR BEST FRIEND IN COLD AND FLU SEASON.

Not only does your gut hold brain cells, it also houses the bulk of your immune cells—70 percent—in the form of gut associated lymphoid tissue, or GALT, which plays a huge part in killing and expelling pathogens. GALT and your gut microbiome—the trillions of bacteria that live, like an immense microbial universe, in your gut—work hard to help you get over what ails you. That’s all the more reason to be careful with the use of antibiotics, which wipe out the good bacteria along with the bad.

10. YOUR GUT CAN BECOME ADDICTED TO OPIATES.

Inside your gut are opiate receptors, which are also found in the brain. The gut is just as susceptible to addiction as the brain and may contribute to the intense difficulty some addicts have trying to kick the habit.

What Causes Hiccups?

iStock/damircudic
iStock/damircudic

The cause of hiccups depends on whom you ask. The ancient Greek physician Galen thought hiccups were violent emotions erupting from the body, while others thought they were a sign of liver inflammation. Today, evidence points to spasms in the diaphragm, the large muscle between the chest and abdomen that aids airflow during breathing. This involuntary contraction can be brought on by a number of things that might irritate the nerves that control the movement of the muscle. A full stomach, heavy boozing, rapid shifts in temperature either inside or outside of the stomach, and certain emotions like shock or excitement are all common culprits.

No matter the cause, the result is the same: The diaphragm spasms and causes us to take a quick breath. The sudden rush of air causes the epiglottis (the flap that protects the space between the vocal cords) to shut and interrupt the breath, which makes the familiar "hic" sound.

WHAT CURES THEM?

The best cure for hiccups also depends on the person you ask. Almost all cures are based on one of two principles: One type works its magic by overwhelming the vagus nerve with another sensation. The vagus nerve is a cranial nerve that innervates the stomach and conveys sensory information about the body's organs to the brain. When distracted by overwhelming information of another sort, it basically tells the brain that something more important has come up and the hiccuping should probably be stopped (vagus nerve stimulation is also used to control seizures in epileptics and treat drug-resistant cases of clinical depression). The other method for curing hiccups is to interfere with the breathing, increasing the amount of carbon dioxide in the blood, and causing the body to focus on getting rid of the of the CO2 and not making hiccups.

Swallowing a spoonful of sugar is probably the most commonly prescribed hiccup cure and falls into the first category. A teaspoon of sugar is usually enough to stimulate the vagus nerve and make the body forget all about the hiccups. Even ardent supporters of the sugar cure disagree if the sugar should be taken dry or washed down with water, though.

If this home remedy doesn't work, and your hiccups are both severe and persistent, you may need to bring out the big guns. For chronic cases like this, doctors sometimes use a cocktail of Reglan (a gastrointestinal stimulant) and Thorazine (an anti-psychotic with sedative properties) to quiet things down. In some cases that resist these drugs, Kemstro, an anti-spasmodic, is also used. Other doctors have used vagus nerve stimulators implanted in the upper chest of patients. The pacemaker-like devices send rhythmic bursts of electricity through the vagus nerve to the brain to keep the hiccup cycle in check.

Many people prefer home remedies to battle their hiccups, which may include holding your breath, gargling ice water, or breathing into a paper bag. While the same people will swear by the treatment they've been using all these years, there's no firm scientific consensus that any of them actually work. But if it helps you, isn't that all that matters?

Have you got a Big Question you'd like us to answer? If so, let us know by emailing us at bigquestions@mentalfloss.com.

An earlier version of this article appeared in 2012.

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