For many patients, the most prescribed medication in Canada may have been wrongfully issued. This drug is used for those with underactive thyroids, the condition known clinically as hypothyroidism. The medication in question is known as levothyroxine, a synthetic version of thyroxine (T4), one of our body’s naturally produced thyroid hormones. Levothyroxine is commonly sold under the name brand names Synthroid and Eltroxin.
Although hypothyroidism is real and affects roughly 20 million Americans,  some patients are being given this medication to treat mild abnormalities with the thyroid hormones, also known as subclinical hypothyroidsim — and it’s not helping.
What is Hypothyroidism?
Hypothyroidism is a condition where one’s thyroid under-produces hormones. The symptoms vary depending on the severity of the deficiency. Issues tend to develop slowly over time.
The thyroid is a small butterfly-shaped gland that sits anteriorly on the lower portion of the neck. The hormones produced by the gland include triiodothyronine (T3) and thyroxine (T4). They work to regulate metabolism and have far effects on digestive function, body temperature, and heart rate.
Hypothyroid symptoms include:
- Sensitivity to cold
- Dry skin
- Impaired memory
- Hoarse voice
- Weight gain
- Muscle weakness and aches
- Joint pain, stiffness, or swelling
- Thinning hair
- Slowed heart rate
- Enlarged thyroid gland (goiter) 
To treat a full-fledged case of hypothyroidism, drugs work to supplement or completely replace the lack of thyroxine (T4) being produced. However, sometimes there are borderline situations, where T4 hormone production seems adequate, but there may be a higher risk of hypothyroidism developing. This is known as subclinical hypothyroidism.
What is Subclinical Hypothyroidism?
In a healthy body, thyroid-stimulating hormone (TSH) is produced by the pituitary gland in the brain. TSH stimulates the thyroid to produce thyroxine (T4.)
Diagnosing hypothyroidism is based on the presence of symptoms and blood tests. Blood tests include measuring thyroid stimulating hormone (TSH) and thyroxine (T4).
High levels of TSH and low levels of T4 would indicate an underactive thyroid.
Subclinical hypothyroidism, on the other hand, is diagnosed when only TSH is found to be elevated, but Symptoms are usually minimal and T4 levels are within the norms .
“The brain probably detects that the thyroid gland is mildly dysfunctional,” says Agoritsas, “and compensates by stimulating it more.” 
If T4 levels are normal, that shows the TSH production is functioning and the body may not need levothyroxine medication.
Should Subclinical Hypothyroidism be Treated like Hypothyroidism?
An international panel of doctors, including Dr. Thomas Agoritsas, an assistant professor of medicine at Hamilton’s McMaster University, says that when it comes to subclinical hypothyroidism, levothyroxine hormones, “consistently demonstrate no clinically relevant benefits for quality of life or thyroid-related symptoms, including depressive symptoms, fatigue, and body mass index.” 
“From what we know,” says Agoritsas, “it’s very likely [levothyroxine treatment] won’t work.” Agoritsas also works at Geneva University Hospitals. 
Dr. Agoritsas’ recommendations were published in the British Medical Journal (BMJ) on May 14th.
The Studies: Does Hormone Treatment Help or Harm?
The panelists analyzed 21 clinical trials with over 2,1000 participants, many of which were over the age of 65. These studies used participants, adults with subclinical hypothyroidism, who were in treated with either thyroid hormone treatment, no treatment, or placebo.
The panel decided to discourage the use of hormone treatment for this form of hypothyroidism due to the lack of benefits, the uncertainty of possible harm, and the burden of administering medication daily and taking frequent blood tests to check the dosage. 
Why Do Doctors Prescribe Medication for Subclinical?
However, it’s very common for doctors to issue medication to treat subclinical hypothyroidism, especially in Canada.
It makes sense for doctors to prescribe medication for an ailment and see if it helps. Especially in the case of thyroid issues, which are easy to check and have vague symptoms that could apply to other diseases. This is the theory of Dr. Deric Morrison, an endocrinologist at St. Joseph’s Hospital in London, Ontario.
“But the evidence is now suggesting for most of those people, treating that number doesn’t make them better,” he concludes.
Agoritsas method is to check the hormone levels of patients with hypothyroid symptoms. If there are no abnormalities in the blood test, he’ll offer other methods of handling the symptoms. If the patient wants to try a short-term trial of levothyroxine treatment, he’ll prescribe it without the expectation of the patient staying on it for life.
It’s important to note it’s inadvisable to stop taking levothyroxine pills without consulting your health care practitioner.
- General Information/Press Room https://www.thyroid.org/media-main/press-room/
- Hypothyroidism (underactive thyroid) https://www.mayoclinic.org/diseases-conditions/hypothyroidism/symptoms-causes/syc-20350284
- Disclosing subclinical thyroid disease. An approach to mild laboratory abnormalities and vague or absent symptoms. https://www.ncbi.nlm.nih.gov/pubmed/10649671
- Thyroid hormones treatment for subclinical hypothyroidism: a clinical practice guideline https://www.bmj.com/content/365/bmj.l2006
- Why doctors warn against routinely treating thyroid issues https://www.cbc.ca/news/health/hypothyroidism-subclinical-1.5138719
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