What Do Thyroid T3 and T4 Numbers Mean?

Last week I talked about your thyroid stimulating hormone, or TSH. It comes from your pituitary gland, and it’s the hormone medical doctors usually use to check to see how well your thyroid is working and to diagnose a thyroid disorder.

The amount of TSH your pituitary sends out is influenced by the levels of two hormones in your blood.

These are called triiodothyronine and L-thyroxine, but it’s easier to remember them by their more common names, T3 and T4 respectively.

These hormones help stimulate your metabolism. Put more simply, they tell your body how fast or how slow it should run. Your energy levels, weight, hair growth, skin texture, mood, sex drive, and body temperature are all affected by your metabolism.

Anyway, your pituitary measures the T3 and T4 levels in your blood and decides how much TSH to send out accordingly.

Where do Thyroid T3 and T4 come from?

T3 and T4 are both made using iodine. Your thyroid makes T4 as well as some T3. Most T3 is made in the liver, amongst other places in your body.

Even though they’re both made using iodine, there’s a difference in how they function. In fact, even though there’s less iodine in a T3 molecule, it stimulates your metabolism four to five times stronger than T4 does.

This might sound technical and confusing, but I promise you it will make sense.

See, if your thyroid isn’t active, your metabolism won’t be stimulated properly. Some underactive thyroid symptoms include hair loss, tired or moody feelings, and loss of sex drive.

Without a healthy thyroid, you won’t have enough T3. Without enough T3, your metabolism won’t be working like it should.

How can we make sure you’re making enough T3?

Your thyroid also produces a hormone called reverse-T3, or rT3. rT3 is like T3’s lazy deadbeat brother in law. He’ll show up, take up space, eat all your food, and not contribute anything good. When your body isn’t producing the T3 it should, rT3 starts building up.

This can cause a metabolic disaster! But if we take a look at the ratio of rT3 to T3 in your tissue, we can bring things back into balance through naturopathic remedies.
Next time we’ll talk about the different thyroid hormones in your body, what they do, and how things can get out of whack.

Until next time, this is Dr. Pat Nardini, ND, putting “Your Wellness First!”