Most conventional doctors rely on TSH as the gold standard to measure thyroid functioning. Many mainstream doctors do not run a full thyroid panel that should at least include Free T4, Free T3, Reverse T3, and thyroid antibodies. Unfortunately TSH alone does not provide a complete picture. If doctors are going to rely on TSH alone, however, they should at least give consideration to the controversy over the TSH normal reference range and consider this when diagnosing patients. Right? We are more than a lab number. It’s up to us to take control of our thyroid health and insist our doctors treat us the patient and not this controversial TSH lab number, even if they look at us like we are CRAZY for questioning them!
The thyroid gland is a little butterfly-shaped gland at the base of our necks. TSH stands for Thyroid Stimulating Hormone, a hormone produced in the pituitary gland in the brain that tells the thyroid how much thyroid hormone to make.
Typically, if there is a low level of thyroid hormone in the body, the pituitary will increase production of TSH to stimulate the thyroid to produce more thyroid hormone. Therefore a high TSH level suggests an underactive thyroid (hypothyroidism), while a low TSH indicates too much thyroid hormone in the body (hyperthyroidism).
In my post “Miscarriage in New York City…Be Thyroid Aware”, I outlined the TSH ranges for pregnancy and provided trimester-specific ranges. In this post I would like to discuss the normal TSH lab standards for non-pregnant adults.
Thyroid Stimulating Hormone
For many years, most mainstream doctors have considered TSH level >10 mIU/L evidence of overt thyroid failure, and levels of 5-10 mIU/L evidence of mild or subclinical hypothyroidism. Many doctors refuse to treat hypothyroidism if a person’s TSH is less than 5 mIU/L even when the patient presents with classic hypothyroidism symptoms. This strict reliance on 5 mIU/L has left many hypothyroid people suffering with debilitating symptoms and yet their doctors refuse treatment.
For over a decade there has been considerable debate about the correct upper limit of the reference interval for TSH. According to the old standards 5.0 mIU/L is the upper limit. This upper number is critical in determining who is diagnosed with hypothyroidism and who is not.
Modern medicine continues to argue within itself on the proper upper limit of the reference range for TSH.
One of the largest studies of thyroid problems in a population is the Whickham Survey, which studied the thyroid levels of 2,779 randomly selected adults living in the town of Wickham in England from 1972-1973 and subsequently followed for 20 years. Data from the twenty-year follow-up published in 1995 demonstrated an increased risk for the development of hypothyroidism once TSH exceeds 2.0 mIU/L.1
The third National Health and Nutrition Examination Survey (NHANES III) screened 17,353 subjects from 1988 to 1994 and excluded those with diseases or factors known to affect thyroid function. In the resultant ‘normal’ population of 13,344 subjects, 95% had TSH levels that fell between 0.3 and 2.5 mIU/L.2,3
These findings supported the establishment of a narrower TSH reference range and a lowering of the upper limit of the range.
The National Academy of Clinical Biochemistry (NACB) in 2002 recommended that the upper limit of the reference range be lowered:4
The recent follow-up study of the Whickham cohort has found that individuals with a serum TSH >2.0 mIU/L at their primary evaluation had an increased odds ratio of developing hypothyroidism over the next 20 years, especially if thyroid antibodies were elevated.
In future it is likely that the upper limit of the serum TSH reference range will be reduced to 2.5 mIU/L.
In 2003, the American Association of Clinical Endocrinologists issued a press release in support of lowering the upper limit of the reference range:5
Until November 2002, doctors had relied on a normal TSH level ranging from 0.5 to 5.0 to diagnose and treat patients with a thyroid disorder who tested outside the boundaries of that range. Now AACE encourages doctors to consider treatment for patients who test outside the boundaries of a narrower margin based on a target TSH level of 0.3 to 3.0. AACE believes the new range will result in proper diagnosis for millions of Americans who suffer from a mild thyroid disorder, but have gone untreated until now.
However in 2012, the Clinical Practice Guidelines for Hypothyroidism in Adults: Cosponsored by the American Association Of Clinical Endocrinologists and the American Thyroid Association recommended 4.12 as the upper limit of normal for TSH.6 (Wait! What happened to the AACE’s press release in 2003 to reset the TSH level to 0.3 to 3.0? Do you see the craziness of all this?)
Thyroid Advocacy To Lower The Upper Limit of TSH
Thyroid advocates and many integrative physicians are fighting to narrow that range. Thyroid doctor Dr. Weston “Wiggy” Saunders posted this important message on his Dr. Wiggy Thyroid MD Facebook page.
Thyroid advocate Mary Shomon, from the About.com Thyroid Disease website, shared this important list of recommended lab tests and optimal ranges on her Thyroid Support Facebook page. Note the optimal TSH range listed.
When I was initially diagnosed with hypothyroidism after the birth of my first son in 2006, I listened to my doctors unquestioningly. I assumed that my doctors were the experts and that they knew everything there was to know about this disease. My doctor was using the old 0.5 to 5.0 TSH lab standard and kept telling me my TSH was normal falling in this range, yet I felt awful. Under my doctor’s care my TSH levels rose to 10.0 mIU/L.
At a TSH of 4.0 I felt sick and tired. By the time my TSH rose to 10.0, I felt like the walking dead struggling to make it through each day.
I even had one doctor who said she only treated a person for hypothyroidism when their TSH rose above 10.0 otherwise it was unnecessary. WHAT?!! I couldn’t function at a TSH of 10. I couldn’t get up from my bed to take care of my young son.
What Should You Do?
What if you have many symptoms of hypothyroidism, but your doctor is testing TSH only and your TSH is “normal”. What should you do?
What if you are being treated for hypothyroidism but you still suffer symptoms and your doctor is insisting your treatment is fine because your TSH is “normal”. What should you do?
Don’t just accept “your thyroid is normal” from your doctor. Insist on a full thyroid panel not just TSH but also Free T4, Free T3, Reverse T3 and thyroid antibodies. Get a copy of your lab results and check your scores yourself, even if your doctor acts like you are crazy (because you are NOT)!
If your doctor won’t do the additional tests and insists on relying on TSH while you suffer symptoms, find a new doctor. Find a doctor who understands you are more than a lab number. There are good thyroid doctors out there. Here is a list of resources to help you locate a great thyroid doctor in your area.
Do NOT settle.
- Vanderpump, M.P., Tunbridge, W.M., French, J.M., Appleton, D., Bates, D., Clark, F., Grimley Evans, J., Hasan, D.M., Rodgers, H., Tunbridge, F. The incidence of thyroid disorders in the community: a twenty-year follow-up of the Whickham Survey. Clin Endocrinol (Oxf) 1995 Jul;43(1): 55-68 ↩
- Hollowell, J.G., Staehling, N.W., Flanders, W.D., Hannon, W.H., Gunter, E.W., Spencer, C.A., Braverman, L.E. Serum TSH, T4, and thyroid antibodies in the United States population (1988 to 1994): National Health and Nutrition Examination Survey (NHANES III). J Clin Endocrinol Metab 2002 Feb;87(2):489-99 ↩
- Lee, S.L. When is the TSH normal? New criteria for diagnosis and management. Lecture presented at 12th Annual Meeting of the American Association of Clinical Endocrinologists (AACE), San Diego, CA, May 14, 2003 (thyroidtoday.com) ↩
- National Academy of Clinical Biochemistry 2002. Laboratory Medicine Practice Guidelines: Laboratory Support for the Diagnosis and Monitoring of Thyroid Disease. Retrieved from: http://www.aacc.org/sitecollectiondocuments/nacb/lmpg/thyroid/thyroid-fullversion.pdf ↩
- American Association of Clinical Endocrinologists (January 2003 Press Release). Over 13 Million Americans with Thyroid Disease Remain Undiagnosed. Retrieved from: www.hospitalsoup.com/public/AACEPress_release-highlighted.pdf ↩
- Clinical Practice Guidelines for Hypothyroidism in Adults: Cosponsored by the American Association Of Clinical Endocrinologists and the American Thyroid Association. Retrieved from: https://www.aace.com/files/hypothyroidism_guidelines.pdf ↩