Hypothyroid 101 provides an overview of what the thyroid does, the main thyroid hormones, the main causes of hypothyroidism, how hypothyroidism is diagnosed, as well as options for having thyroid blood tests done.
The Thyroid Gland
The thyroid is butterfly-shaped gland situated in the middle of the lower front part of the neck. While it isn’t very big, it plays a very important role in the regulation of metabolism which is the process by which the food we eat is converted to energy.
When the thyroid doesn’t function properly, it affects metabolism. In the case that the thyroid is underactive (hypothyroid) this results in a slowing of everything from heart rate, our ability to generate heat to stay warm, for muscles to do work, and for us to think properly and process information.
The Two Main Thyroid Hormones – T4 and T3
The thyroid produces two main hormones, T4 (thyroxine) and T3 (triiodothyronine). When it’s working properly, 93% of the thyroid hormone produced by the body each day is T4, and only 7% is T3 [1]. The thyroid manufactures ~85mcg of T4 and 6.5mcg of T3 per day [1], which is a T4 to T3 ratio of 13:1.
T4 is the inactive form of thyroid hormone and has four molecules of iodide bound to it. When it becomes activated, it loses one of the iodides and becomes T3, which is the active form.
In its free, unbound form, thyroxine is known as free T4 (abbreviated fT4) and in its free, unbound form triiodothyronine is known as free T3 (abbreviated fT3).
The production of T4 and T3 in the thyroid is regulated by the pituitary gland, but the signal for the pituitary gland to tell the thyroid gland to make thyroid hormones comes from the hypothalamus region of the brain. The hypothalamus releases a hormone called TRH (Thyrotropin-Releasing Factor) that acts on the pituitary gland, causing it to release a hormone called TSH (Thyroid Stimulating Hormone). It is TSH released from the pituitary gland that acts on the thyroid gland, causing it to release thyroxine.
- from [2] The Merck Manual of Medical Information (1997)
Hypothyroid – how it is diagnosed
In Canada and many places in the US, the standard screening test for abnormal thyroid function, including hypothyroid, is a blood test measuring thyroid stimulating hormone (TSH), which is a pituitary hormone.
If TSH results falls within normal range, no testing of thyroid hormones occurs. The thyroid response to TSH is presumed to be normal.
Central Hypothyroidism occurs when there is a problem with either the hypothalamus or the pituitary gland.
On lab tests, a low TSH and low free T4 indicates central hypothyroidism and this is often treated by prescribing medication, including T3 containing medications.
Primary hypothyroidism is where there is no abnormality in the hypothalamus or the pituitary gland. It is diagnosed when there is high TSH, and normal or low free T4.
Hypothyroid – main causes
In the developed world, the most common form of primary hypothyroid in is Hashimoto’s disease. In developing countries, it is mostly caused from a lack of iodine in the diet. Other causes of hypothyroid includes the trauma from surgery to remove a benign or cancerous tumour, or the result of radioactive iodine treatment for overactive thyroid.
Hashimoto’s disease is the most common cause of hypothyroid in the West. It is an autoimmune disorder where the body’s immune system, specifically the lymphocytes attack the thyroid. In response to this attack, the thyroid produces antibodies, specifically thyroperoxidase antibodies (TPO-ab) and thyroglobulin antibodies (TG-ab) [3]. A diagnosis of Hashimoto’s is made based on both the presence of symptoms of hypothyroidism, as well as the presence of TPO-ab or TG-ab.
One of the main challenges with getting diagnosed as hypothyroid is that many of the early symptoms of hypothyroidism are non-specific — meaning they can have several different causes.
In a post-pandemic world of telephone doctor appointments, such vague symptoms may seem too inconsequential to bring up.
Below is a downloadable checklist that can help you have a conversation with your doctor.
Symptoms such as body aches, joint pain, fatigue, feel chilled, weight gain, frequently being constipation, having dry skin don’t seem ‘serious’ enough to make an appointment with one’s doctor and could be due to a number of different causes from not eating well, to having a virus, and are very often discounted as being due to “age”. Even forgetfulness and depression which are known symptoms in more advanced hypothyroidism are often attributed to aging.
Hypothyroid – getting evaluated and diagnosed
As outlined in an earlier article, in British Columbia unless a person is of advanced age, has a family history or personal medical history of thyroid disease or another autoimmune disorder, takes medications such as lithium or amiodarone, or is from a developing country with iodine deficiency, they do not even qualify for TSH testing unless they display the specific symptoms listed in Table 1, below [4].
- Table 1: Signs and Symptoms of Hypothyroidism (from [4])
One drawback to the above approved checklist is that it does not include some of the well-documented symptoms of hypothyroidism, such as non-pitting edema of the lower legs and ankles, a puffy swollen face, an enlarged tongue (with or without scalloped edges), loss of the outer third of eyebrows, or having pale or bluish lips.
Even if one has a blood test for TSH, if it comes back at the high end of the normal range, no further testing is done [4].
Without a person having known risk factors, or having symptoms that appear in the official list in the Guidelines and Protocols [4] (Table 1, above), diagnostic tests may not be requisitioned unless or until a person becomes sicker and the reason for this is explained below, in the section about ordering lab tests.
To help people have an informed discussion with their doctor, below is a 2-page downloadable, fillable checklist that contains a list of common hypothyroid symptoms, along with a simple explanation of what that symptom is. For example, in this checklist “periorbital edema” is explained as ‘swelling under eyes.’
Please note that this checklist list is not exhaustive and is NOT intended to be used for self-diagnosis purposes. It is only provided so that people who think they may have symptoms of hypothyroidism can consult with their doctor, and discuss the matter with them. Remember, only a medical doctor can diagnose and treat.
Signs and Symptoms of Hypothyroidism – 2-page downloadable and fillable checklist
Thyroid Panel Lab Tests – 3 options to diagnose hypothyroid
[updated: November 3, 2022]
In Canada, there is no such thing as a standard “thyroid panel,” although naturopaths offer thyroid assessment panels on a client-pay basis. Medical doctors can order thyroid function tests based on the guidelines of their specific province, and naturopaths can order different thyroid assessment panels, depending on the province they are located in.
1. Medical Doctor (MD)
Thyroid function blood tests can be ordered by medical doctors (MDs) including family practice physicians, general practitioners (GPs), and specialists such as Endocrinologists and the cost of testing will be covered by the provincial health plan if it meets their guidelines.
In most provinces in Canada, a requisition needs to be written by a licensed medical doctor for the cost of the test to be covered by the provincial health plan. In New Brunswick and Nova Scotia Health authorities and lab regulators have placed restrictions on how lab tests can be ordered, and patents are charged fees to order them privately.
In Ontario, Saskatchewan and British Columbia, the following guidelines apply;
- In Ontario: thyroid tests that are covered are outlined in the Schedule of Benefits for Laboratory Services, July 1, 2020.
- In Saskatchewan: Saskatchewan Disease Control Laboratory, Laboratory Testing Guidelines for the Diagnosis and Monitoring of Thyroid Disease, September 24, 2018
- In British Columbia: the BC Guidelines & Protocols Advisory Committee, Thyroid Function Testing in the Diagnosis and Monitoring of Thyroid Function Disorder, October 24, 2018.
Furthermore, in British Columbia, physician-ordered lab tests must be requisitioned in accordance with the Laboratory Services Act to be covered by MSP (Medical Service Plan). Doctors are in a very challenging position in BC as MSP can seek recovery for lab-test cost from a doctor if they feel that the test(s) ordered were not clinical justified.
Most physician-initiated lab test investigation for hypothyroid begins with a TSH test. One reason for this is to rule out Central Hypothyroidism which is where there is a problem with either the hypothalamus, or the pituitary gland. As explained above, a low TSH will likely result in a free T4 test being requisitioned. If free T4 is also low, then T3 medication or some other type of medication might be prescribed, or the person referred to an endocrinologist.
-
-
- TSH: $9.90
- free T4: $12.12
- free T3: $9.35
- thyroperoxidase antibody (TPO-ab): $20.22 (payable only for possible autoimmune thyroid disease)
- thyroglobin antibody (TG-ab): $27.90 (only performed as an adjunct to thyroglobulin measurement for the conditions such as thyroid tumors, cancer, etc.)
- reverse T3: uninsured test
-
- from http://www.bccss.org/bcaplm-site/Documents/Programs/laboratory_services_schedule_of_fees.pdf
2. Naturopathic doctor (ND)
-
- TSH
- Free Thyroxine (FT4)
- Free Triiodothyronine (FT3)
- Reverse T3
- Thyroperoxidase Antibody (TPO-ab)
- Anti-Thyroglobulin (TG-ab)
-
- TSH: $9.90
- free T4: $12.12
- free T3: $9.35
- thyroperoxidase antibody (TPO-ab): $20.22 (payable only for possible autoimmune thyroid disease)
- thyroglobin antibody (TG-ab): $27.90 (only performed as an adjunct to thyroglobulin measurement for the conditions such as thyroid tumors, cancer, etc.)
-
- TSH
- Free Thyroxine (FT4)
- Free Triiodothyronine (FT3)
- Thyroperoxidase Antibody (TPO-ab)
Reverse T3 and Anti-Thyroglobulin (TG-ab) are not available.
3. Patient-Pay
Final Thoughts
Determining whether the symptoms one has may be related to their thyroid, and going about getting tested can be challenging. It is my hope that by providing the information in this article, you can have an informed discussion with your doctor.
If you would like more information about how I can support you in your goal of improved health, please send me a note through the Contact Me form above.
To your good health!
Joy
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References
- Jonklaas J, Bianco AC, Bauer AJ, et al, Guidelines for the treatment of hypothyroidism: prepared by the American thyroid association task force on thyroid hormone replacement. thyroid. 2014 Dec 1;24(12):1670-751.
- Berkow, R., Beers, M. H., & Fletcher, A. J. (1997). The Merck Manual of Medical Information. Whitehouse Station, N.J.: Merck Research Laboratories.
- Puszkarz, Irena, Guty, Edyta, Stefaniak, Iwona, & Bonarek, Aleksandra. (2018). Role of food and nutrition in pathogenesis and prevention of Hashimoto’s thyroiditis. https://doi.org/10.5281/zenodo.1320419
- BC Guidelines & Protocols Advisory Committee, Thyroid Function Testing in the Diagnosis and Monitoring of Thyroid Function Disorder, October 24, 2018
- Laboratory Services Act, Laboratory Service Regulation, October 1, 2015 (last amended September 20, 2020 by B.C. Reg. 263/2020)
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