Do you ever think, “I’m tired and I can’t lose weight. I wonder if it’s my thyroid?” Fatigue and weight gain have a lot of reasons, and low thyroid hormone is one of them. But most doctors will only do one test for thyroid function. However, there are a number of thyroid blood tests that can shed light on your thyroid health, and many doctors will not do them. Here is an explanation of several of them so you know what they show.

The main “thyroid” blood test is the thyroid stimulating hormone, or “TSH”. This is almost always what is ordered by most doctors. Fun fact: TSH doesn’t actually measure thyroid hormone! TSH is a hormone made by the pituitary gland, and it goes to the thyroid to tell it to make more thyroid hormones. It is pretty sensitive to what the thyroid is doing, though.

TSH is what I call a “backwards” test. When it goes up, your thyroid hormone levels are low. When it goes down, it means you have high thyroid hormone levels. This is not intuitive, but here’s why. When your thyroid gland is sluggish, and not making enough hormone, your pituitary gland senses that and starts to yell at the thyroid: “Make more hormone!” The lower the hormones being produced, the more TSH is made. It’s like when your kids have a messy room. You start to yell louder and louder “clean up your room!” until they start doing what they are supposed to be doing.

Most labs have a reference range of around 0.4 – 4.5 for TSH. However, many thyroid experts believe the TSH shouldn’t be over 2.5 or 3.0. If it is between 3.0 and 4.5, it is sensing something isn’t quite right with the thyroid. So optimal TSH is typically thought to be 0.4 – 2.5.

There are other thyroid tests that often should also be tested. Free T4 and free T3 are the actual hormones that the thyroid is making. Sometimes the TSH is borderline but free T4 and free T3 are normal, which is reassuring. Bear in mind if you are taking a porcine thyroid or a T3 product like Cytomel, your free T3 level will be elevated for 4-6 hours after taking your medication. Check with your doctor about whether you should take your medication before your lab draw.

Reverse T3 is another thyroid level that can be very helpful. This is a form of T3 that the thyroid makes, but it is a biologically inactive form of T3. Essentially, it is formed wrong, and it looks kind of like T3 but it won’t fit in the T3 receptors. So it doesn’t do anything. Reverse T3 is make much more often when you are under stress. If your reverse T3 is over 15, you likely have stress that is affecting you and that needs to be addressed.

The last thyroid labs are also often ignored by primary care physicians. Everyone that has a thyroid issue should have thyroid antibodies checked at least once. These include thyroid peroxidase antibodies (“TPO”) and thyroglobulin antibodies (“TgAb”). Millions of people have these antibodies that are autoimmune, meaning their own immune system is confused and produces antibodies against their own thyroid gland. Over time, this damages the thyroid. Also, if you have one autoimmune condition, you are at higher risk to have another (such as multiple sclerosis, rheumatoid arthritis, celiac disease, psoriasis, and others).

Autoimmunity can be treated by an integrative or functional medicine practitioner and typically includes anti-inflammatory supplements, an anti-inflammatory diet, and healing any gut inflammation present.

If you are on thyroid medication, always follow your provider’s advice on dosing and do not take supplements or other natural “thyroid” medications without consulting with your provider, as some over the counter preparations will affect your medication and your levels.

Ask your functional medicine provider about full thyroid blood testing today!