What is TSH?
TSH is produced by the pituitary gland and is part of the body's system to maintain correct amounts of the thyroid hormones thyroxine (T4) and triiodothyronine (T3) in the blood and to help control the rate at which the body uses energy.
The thyroid-stimulating hormone (TSH) test is the most common test for evaluating thyroid function and/or symptoms of a thyroid disorder.
Why Test TSH?
Unless this is ordered as a retest or for a specific reason, we recommend ordering TSH as part of a health test. You may want to test TSH along with other thyroid markers for these reasons:
Symptoms
You have symptoms of thyroid disorder, even if other thyroid results are within range
Health check
As part of a general health and wellness check to screen for thyroid disorders
Monitoring
To monitor a thyroid disorder, your need for medications, and the progression of your illness. If you have just changed your dose of thyroid medication, wait 6-8 weeks before testing TSH again in order to get an accurate result.
Fertility
To help to diagnose and investigate fertility problems in women
What do the results mean?
Whether it is high or low, an abnormal TSH indicates too much or too little thyroid hormone, but it doesn’t show why. Further testing is needed for this purpose. A normal TSH value does not necessarily rule out thyroid imbalances. They must be interpreted alongside your other thyroid markers and a person’s current symptoms and medical history.
If your TSH is normal and you have symptoms that could be attributed to thyroid problems, it is important to investigate further. Consult your doctor to discuss your results and symptoms. Discuss any relevant lifestyle, nutrition, or dietary changes with your nutritionist to find out the root cause of the problem.
What are the symptoms of hyperthyroidism?
Common symptoms of hyperthyroidism (an overactive thyroid function) include unwanted weight loss even when your food intake stays the same, rapid heartbeat, irregular heartbeat, nervousness, anxiety, irritability, tremor, enlarged thyroid gland (called goiter, which can be seen as a swelling at the base of your neck), sweating, changes in menstrual patterns, increased sensitivity to heat, changes in bowel movement especially more frequent ones, fatigue, muscle weakness, difficulty sleeping, thinning skin and brittle hair.
What are the symptoms of hypothyroidism?
Common symptoms of hypothyroidism (an underactive thyroid) include fatigue, feeling cold, often cold hands, feet and tip of nose, constipation, dry skin, weight gain or difficulty losing weight, puffy face, hoarseness, muscle weakness, stiff and achy muscles, slowed heart rate, dry and thinning hair, poor memory, and depression.
What causes low TSH?
Low TSH most commonly means that a person has hyperthyroidism or an overactive thyroid. Normally hypothyroidism presents with normal to high TSH and normal to low T4 and T3. However, this is not true for everyone. In rare cases, patients with hypothyroidism present with low TSH as well as low T4, due to pituitary failure.
Common symptoms of hyperthyroidism (an overactive thyroid function) include; unwanted weight loss even when your food intake stays the same, rapid heartbeat, irregular heartbeat, nervousness, anxiety, irritability, tremor, enlarged thyroid gland (a goiter that can be seen as a swelling at the base of your neck), sweating, changes in menstrual patterns, increased sensitivity to heat, changes in bowel movement especially more frequent ones, fatigue, muscle weakness, difficulty sleeping, thinning skin and brittle hair.
Common symptoms of hypothyroidism (underactive thyroid) include fatigue, feeling cold, often cold hands, feet, and the tip of the nose, constipation, dry skin, weight gain or difficulty losing weight, puffy face, hoarseness, muscle weakness, stiff and achy muscles, slowed heart rate, dry and thinning hair, poor memory, and depression.
Many factors affect TSH results, including age, ethnicity, gender, medication use, and BMI. In America, the average TSH level is 1.5 in patients without known thyroid disease, and many doctors find that their patients feel their best between the range 1.5-2 mU/L. Functional labs, which work with
What causes high TSH?
A high TSH alongside low free T4 may indicate an underactive thyroid gland and some kind of thyroid dysfunction. High TSH may mean that a person has hypothyroidism (low thyroid function). It may indicate that a person’s thyroid hormone medication needs adjusting, or that there is a problem with the pituitary gland. Sometimes TSH is temporarily elevated due to stress and/or infections.
The most common cause of hypothyroidism is Hashimoto’s thyroiditis, an autoimmune disease. We strongly recommend that you do a full thyroid panel to thoroughly investigate the cause of your high TSH.
Common symptoms of hypothyroidism (underactive thyroid) include fatigue, feeling cold, often cold hands, feet, and the tip of the nose, constipation, dry skin, weight gain or difficulty losing weight, puffy face, hoarseness, muscle weakness, stiff and achy muscles, slowed heart rate, dry and thinning hair, poor memory, and depression.
More Information
The normal range for TSH is controversial. Most labs still consider the upper range to be between 4 and 5 mU/L. In 2003 the American Association of Clinical Endocrinologists recommended lowering the reference range to 0.3-3 mU/L but clinical guidelines were not changed. In America, the mean TSH level is 1.5 in patients without known thyroid disease and many doctors find that their patients feel their best at an upper limit of 1.5-2 mU/L. Functional labs, which work with reference levels to obtain optimal health, have their upper limit of 1.5-2 mU/L.
It’s important to note that a single thyroid marker cannot give a clear picture. A normal TSH result does not rule out thyroid problems. Thyroid markers must be interpreted alongside your other thyroid markers, current symptoms, and medical history.
Instructions
No advance preparation is required for this test.
On the day
Remember to take I.D. with you when going to take a test. Do not take your thyroid medication until after you have taken this test.