CLOSE
iStock
iStock

11 Eye-Opening Facts About the Thyroid

iStock
iStock

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.

nextArticle.image_alt|e
Photo illustration by Mental Floss. Images: iStock.
arrow
science
What's Really Happening When We See 'Stars' After Rubbing Our Eyes?
Photo illustration by Mental Floss. Images: iStock.
Photo illustration by Mental Floss. Images: iStock.

It's likely happened to you before: You start rubbing your eyes and almost immediately begin seeing colors, specks, and swirls from behind your closed lids. So what's happening when you see these 2001-esque "stars"? Do they only occur upon rubbing? Does everyone experience them?

Before we can get to what causes the lights, we need to understand a bit about how the eyes work. Angie Wen, a cornea surgeon at New York Eye and Ear Infirmary of Mount Sinai, tells Mental Floss that the retina—the innermost layer of the eye—consists of millions of cells, or photoreceptors. These cells, she says, "are responsible for receiving information from the outside world and converting them to electrical impulses that are transmitted to the brain by the optic nerve. Then, the brain interprets them as images representing the world around us."

However, what we see doesn't just stop there. Sometimes "we see light that actually comes from inside our eyes or from electric stimulation of the brain rather than from the outside world," Wen says. "These bursts of seemingly random intense and colorful lights are called phosphenes, and appear due to electrical discharges from the cells inside our eyes that are a normal part of cellular function."

People have been writing and theorizing about phosphenes for thousands of years. Greek philosophers thought the bursts of light were the result of fire inside our heads: "The eye obviously has fire within it, for when the eye is struck fire flashes out," wrote Alcmaeon of Croton (6th–5th century BCE), a philosopher and early neuroscientist, of the swirls and specks someone sees after getting a blow to the head. A century later, Plato—who believed that a "visual current" [PDF] streamed out of the eye—wrote that "Such fire as has the property, not of burning, but of yielding a gentle light they [the Gods] contrived should become the proper body of each day."

Plato's take was still the dominant one through the Middle Ages. Eventually, Newton (1642–1727) theorized a concept that's more in line with what's believed today about these strange sparkly visions: The phenomenon is due to light that's produced and observed when pressure and motion is placed on the eyes.

Eleonora Lad, an associate professor of ophthalmology at Duke University Medical Center who has a background in neuroscience, explains exactly why eye rubbing generates these visions: "Most vision researchers believe that phosphenes result from the normal activity of the visual system after stimulation of one of its parts from some stimulus other than light," including putting external pressure on the eyes. (Interestingly, due to retinal damage, blind people can't see phosphenes caused by pressure, but they can see them when their visual cortex is electrically stimulated. In hopes of turning this phenomenon into improved vision for the blind, scientists have developed a cortical visual prosthesis, implanted in the visual cortex, that generates patterns of phosphenes. The device has been approved by the FDA for clinical trial.)

As Alcmaeon rightly pointed out, there are causes for the bursts of light beyond just rubbing your eyes: Getting hit in the eye can produce this phenomenon—as can a sneeze, a surprisingly powerful event that tends to clamp our eyes shut, Wen says.

Receiving an MRI or EEG may also trigger it. MRIs, for example, produce a changing magnetic field which can stimulate the visual cortex, making a person see these flashing lights. When it comes to an EEG, depending on the brain stimulation frequency band (Hz) used, some patients experience the phenomenon when closing their eyes, which is believed to come from retinal stimulation during the process.

And the activity doesn't only happen on Earth; astronauts in space have also been known to experience them. As reported in 2006 in the journal Vision Research, "over 80 percent of astronauts serving in today's NASA or ESA (European Space Agency) programs have perceived phosphenes at least in some missions and often over several orbits." They're mainly attributed to interactions between the eye and cosmic ray particles in space, outside the Earth's protective magnetic field.

No matter the cause, the bursts of light are perfectly normal—but that doesn't mean you should engage in excessive eye rubbing. Wen says ophthalmologists advise against rubbing your eyes or applying vigorous pressure; according to Lad, too much rubbing may be damaging to the cornea and lens or "result in a loss of fatty tissue around the eyes, causing the eyes to look deep-set."

nextArticle.image_alt|e
iStock
arrow
science
Why Your Knuckles Make That Satisfying Cracking Sound, According to Science
iStock
iStock

Scientific curiosity is not always burdened by matters of great consequence. Over the years, considerable money and time has been applied to matters involving facial recognition between sheep, whether the flow of urine is impeded by someone watching you pee, and whether humans can capably swim in a pool full of syrup. (They can, almost as well as water.)

Now, researchers from Stanford University and Ecole Polytechnique in France have turned the roving eye of science to the phenomenon of knuckle-cracking. According to Gizmodo, a computer simulation was created to confirm an earlier theory that the audible noise that comes from the human hand after putting pressure on the knuckle was the result of gas bubbles popping inside the finger joint.

Conclusion: Probably true.

The study, published in Scientific Reports, demonstrated that microscopic bubbles inside the lubricating synovial fluid of the joint collapse when a knuckle-cracking session commences. To use an imperfect analogy, the cavitation bubbles are like the body’s Bubble Wrap. Popping them produces an audible—and for many, a very pleasing—sound.

To compile data, researchers took geometric representations of the joint's movements during a cracking session and turned them into mathematical equations. (Imaging has not been shown to be very productive in this field, as the crack takes only about 300 milliseconds and is not easily visualized.) The software models demonstrated that pressure shifts in the joint fluid increase pressure on the gas bubbles. Unlike packing material, however, the gas bubbles don't really perforate—they experience a partial collapse but remain suspended in the joint.

So does this solve the mystery surrounding cracked knuckles? Not entirely. Because it was a simulation, there's a possibility of mathematical error. Proponents of alternative theories—that it's not bubbles collapsing but bubbles being created that produce the noise—feel there's more work to be done. We can only hope a complete understanding will come in our lifetime. Fingers crossed. And cracking.

[h/t Gizmodo]

SECTIONS

arrow
LIVE SMARTER
More from mental floss studios