Why You Still Have Hypothyroid Symptoms Despite Normal TSH

In Canada, doctors rely on the Thyroid Stimulating Hormone test (TSH) to determine if your symptoms are due to hypothyroidism. Unfortunately, you can still have hypothyroid symptoms even when your TSH results are “normal”, which can severely impact your health and quality of life. 

The thyroid makes and stores the thyroid hormones T4 and T3 that affect nearly every cell in your body, and the varied symptoms attributed to hypothyroidism reflect that. 

Common symptoms your doctor may look for include fatigue, weight gain, depression, hair loss, constipation, menstrual irregularities, and lowered body temperature, but there are many more! You must also look out for combinations of symptoms like poor circulation, muscle cramps, lowered immunity, slow wound healing, low stomach acid (indicated by poor digestion of protein, mineral deficiencies, risk of parasitic infection and food poisoning), dry skin, swollen face, and the loss of the outer third of your eyebrows.

TSH is produced by the pituitary gland in your brain in response to how much thyroid hormone is in your bloodstream. If there isn’t enough, the pituitary will produce more TSH to tell thyroid peroxidase (the enzyme that makes thyroid hormone in the thyroid) to produce more. And if there is too much, it will produce less TSH to down-regulate the signal to the thyroid.

In theory, TSH tells us when this feedback loop isn’t working and is causing hypothyroidism, but doctors are expecting a lot from this test: it over-generalizes and ignores many other reasons you may have low thyroid symptoms.

Reasons you may have thyroid symptoms even though your TSH levels are “normal”:

  • The pituitary which produces TSH is dysfunctional and does not produce enough TSH even though there are low levels of thyroid hormone in circulation.This is considered secondary hypothyroidism.
  • The testing margins of “normal” TSH are too wide for optimal health, resulting in subclinical hypothyroidism.
  • Under-conversion of T4 to the active T3 form, which happens due to certain medications, high cortisol levels (stress!), high carbohydrate / low protein diets, selenium deficiency and kidney/liver dysfunction.
  • Elevated or decreased thyroid binding globulin (TBG) that transports thyroid hormone while in circulation.
  • Elevated levels of reverse T3  which displaces active T3 thyroid hormones from cellular receptors, and is caused by stress, inflammation, low calorie diets, infections and kidney/liver dysfunction.
  • Autoimmunity in the form of Hashimoto’s thyroiditis where the body attacks thyroid peroxidase (the enzyme that makes thyroid hormone) or thyroglobulin (a protein found in the thyroid). Approximately 90% of primary hypothyroidism is autoimmune and caused by Hashimoto’s thyroiditis.

As our doctors rely on a single test such as TSH to determine hypothyroidism, misdiagnosis is common. The TSH test is an indicator of pituitary production, and cannot be relied upon as way to measure the effectiveness of the thyroid gland which it regulates. If you are experiencing thyroid symptoms despite a “normal” TSH level, request your Free T4, Free T3, and thyroid antibodies be tested. You may need to visit a Naturopath to get these tests done.