5 Essential Thyroid Tests for Women

If you are experiencing some of the following symptoms, it may be worth having your thyroid tested to rule out thyroid hormone imbalances:

  • Very slow or very fast heart rate
  • Weight gain or difficulty losing weight (or rapid weight loss)
  • Change in menstrual cycles (irregular periods, heavy periods)
  • Always feeling very cold or overly hot (or going from one extreme to the next)
  • Fatigue
  • Hair loss
  • Elevated LDL cholesterol level
  • Depression

5 Essential Thyroid Tests to ask for:

  1. TSH (thyroid stimulating hormone)
  2. Free T4
  3. Free T3
  4. TPO-antibodies & TG-antibodies
  5. Reverse T3

Understanding Your Test Results

1. TSH is short for thyroid-stimulating hormone, a hormone made by the pituitary gland (located in the brain) which tells the thyroid what to do. Think of it as the knock on the door. If the thyroid is not doing it’s job, the pituitary will knock more loudly (elevated TSH) whereas if the thyroid is working optimally, the knock will be very light (lower TSH). As you can see, TSH is not made in the thyroid meaning it’s an indirect way of looking at thyroid function.

High levels of TSH may indicate hypothyroidism (i.e. underactive thyroid), a pituitary gland tumor, or inadequate thyroid hormone medication in the treatment of a preexisting condition. Low levels of TSH may indicate hyperthyroidism (i.e. overactive thyroid), damage to the pituitary gland, too much thyroid medication in the treatment of a preexisting condition, or pregnancy in the first trimester.

  • Normal Range: 0.4-5 mIU/L
  • Optimal Range: 0.4 -2.5 mIU/L
  • Hypothyroidism = TSH > 5 mIU/L
  • Hyperthyroidism = TSH < 0.4 mIU/L

2. Free T4: T4 is the main hormone produced by the thyroid so it’s the most direct way at looking at actual thyroid gland function. Keep in mind that T4 is a very weak, mostly inactive hormone that’s main purpose is to be converted into T3 (see below).

  • Normal Range: 9-22 pm/L
  • Optimal Range: 14-18 pm/L
  • Hypothyroidism = < 9 pm/L
  • Hyperthyroidism =  > 20 pm/L

3. Free T3: is made from T4 throughout the body but mostly in the liver. T3 is the most active form of thyroid hormone and is responsible for giving us energy, revving up our metabolism, keeping us warm and with hair on our head. It’s vital to look at T3 hormone levels in order to gauge if there is thyroid dysfunction because you can have normal TSH and T4 levels but if you aren’t converting well to T3 you can still have symptoms of thyroid imbalance.

  • Normal Range: 3.4-5.9 mIU/L
  • Optimal Range: 4.5-5.5 mIU/L
  • Hypothyroidism =  <3.4
  • Hyperthyroidism =  > 6

4. Thyroid Antibodies (TPO and TG): Thyroid peroxidase (TPO), an enzyme found in the thyroid gland, plays a key role in the production of thyroid hormones. A TPO test detects antibodies against TPO in the blood, the presence of which suggests that the cause of thyroid disease is an autoimmune disorder (e.g. Hashimoto’s or Grave’s disease).

  • Normal Range: < 35 kIU/L
  • Auto-immune disease (e.g. Hashimoto’s or Graves’s) > 35 kIU/L

5. Reverse T3: is essentially a “dud” hormone that is made when the body is under stress. A small percentage of our T4 hormone is always converted to reverse T3 in order to prevent the body from being overstimulated by T3. However, in certain conditions, especially with higher stress and cortisol hormone levels, the body can convert too much T4 into reverse T3 which essentially blocks other thyroid hormones from doing their job.

  • Normal Range = < 9-24 ng/dL
  • Optimal Range = less than 18 ng/dL

These tests are all done through a simple blood test which your MD can request. Naturopathic Doctors are also able to run these tests which will cost approximately $100.