My memory of examining the thyroid gland in gross anatomy goes something like this:
“Is that it?” Points to indistinguishable blob of tissue in the neck. “No, I think this is it.” Points to another indistinguishable blob of tissue. “Oh.” The end.
I never really appreciated the thyroid until I lost mine and found out all that it actually does for you. And guess what? It’s super important. I mean, not important like your spleen or pancreas, but more important than one of your kidneys (you do have a spare).
A friend of mine noted recently how he’s been hearing about more and more instances of thyroid illness and asked me if I thought is was on the rise. I’m not sure he was relieved when I told him he’s just getting old. But as a fellow Hey-what’s-this-extra-lump-in-my-neck club member, I know we’re not alone. As many as 50% of people in the community have microscopic nodules, 15% have palpable goiters, and 5% of women have overt hypothyroidism or hyperthyroidism (Reference).
As friends and family are continually
pestering asking me what the thyroid is for and how things have changed since mine was stolen removed due to cancer, I thought I’d share my new found insight. (WARNING –> lots of sciency terms used below)
The thyroid gland is found in the front of your neck, right here:
Take a good hard look at that drawing doctors – when I say I’ve got a lump on my thyroid do not point at the larynx and say “You mean this?” It does not inspire confidence.
It’s an endocrine gland that basically controls how quickly the body uses energy, makes proteins, and controls sensitivity to other hormones. The thyroid produces 2 main hormones: triiodothyronine (T3) and thyroxine (T4). About 90% of thyroid secretions are T4 and the blood normally contains more than a week’s supply of these hormones.
Hormone output is directly regulated by thyroid stimulating hormone (TSH), which is produced by the anterior pituitary gland (in the brain). The release of TSH is regulated by another hormone released by the hypothalamus (also in the brain). So when low levels of thyroid hormones are detected by the hypothalamus it sends a message to the pituitary which then releases TSH, which in turn causes the thyroid gland to release more T3 and T4 (still awake?).
Thyroid hormones can easily cross cell membranes, and they affect almost every cell in the body where they bind to (1) receptors in the cytoplasm, (2) receptors on the surfaces of mitochondria, or (3) receptors in the nucleus. In the mitochondria they increase the rate of ATP production. In the nucleus the hormones activate genes that control the synthesis of enzymes involved with energy transfer and utilization.
BIG PICTURE –> thyroid hormones act to increase the metabolic rate of the cell.
BIGGER PICTURE –> thyroid hormones act to regulate your overall metabolism. They also affect the growth rate and function of many other systems (Table 1).
So, when you no longer have a thyroid gland (or it just isn’t working) you need to take a synthetic version of T4 every day (T4 is converted to T3 by the kidneys, liver, and other organs so T3 doesn’t need to be artificially replaced). Otherwise you get hypothyroidism. The symptoms of hypothyroidism are collectively known as myxedema and include subcutaneous swelling, dry skin, brittle nails, hair loss, low body temperature, muscular weakness, muscle cramps, slowed reflexes, difficulty losing weight, mood swings, and brain fog (yes – that is a technical term).
These signs and symptoms have been recently confirmed by what we’ll call “natural experiment”, but what Genevieve might call “inhumane torture.”
Hypothyroidism is intentionally induced in individuals undergoing RAI treatment or Thyroglobulin (Tg) testing. Tg is a protein only produced by thyroid cells and thyroid cancer cells so it acts as a good cancer maker (one wants these levels to be near undetectable). It’s tested a couple times a year for the rest of a person’s life.
Another fun challenge faced by thyroid cancer patients is maintaining low levels of TSH. This hormone can cause stray thyroid cells to grow, thus potentially increasing the risk of recurring cancer. In a healthy person with a normal thyroid, TSH levels should be about 0.4 to 5.0 mIU/L. In a cancer patient suppressive therapy is used to keep TSH levels around 0.01 to 3.0 mIU/L. This is a delicate balancing act because low levels of TSH can increase the chances of bone loss and heart arrhythmia.
As my own Tg levels need to be tested in a couple of weeks I am not looking forward to the recurrence of “going hypo” (friends are pre-warned). However this is something that I (and lots of other people) will have to get used to until science can grow new thyroids. (Coming soon to a hospital near you?)
And don’t forget folks we are always looking for fun questions to answer and experiments to try. Have a nagging question? Leave a comment on the “Science questions go here” page – it’s where all the cool science questions hang out!