Treating Hashimoto's Thyroiditis With a Normal TSH

Part of the Controversy Lies in What a Normal TSH Is

Blood Sample Tube in Hand
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You may find yourself (or a loved one) in a situation that affects many other people with a thyroid condition: You have Hashimoto's disease (meaning you have positive thyroid peroxidase (TPO) antibodies), but your thyroid stimulating hormone (TSH) falls within the normal reference range.

Even more, you may be experiencing one or more potentially hypothyroid-related symptoms like fatigue, weight gain, brain fog, depression, swelling, or achy muscles—and wonder whether treatment is warranted.

The truth of the matter is that treating Hashimoto's disease in light of a normal (or mildly elevated TSH) is a somewhat controversial, grey area of medical care.

What Is a Normal TSH?

The vast majority of doctors who treat thyroid disease believe that having Hashimoto's disease, as shown by elevated thyroid peroxidase antibodies (TPOAb) or thyroid biopsy results, is not enough reason to treat you, as long as your thyroid stimulating hormone (TSH) test result puts you within the "normal" reference range.

The problem is that the "normal" TSH reference range is disputed among experts, some citing that 4.5 milli-international units per liter or mU/L is the highest end of normal, whereas others believe that anything above 2.5mU/L is high.

Despite this debate, for all intensive purposes, most laboratories still cite the normal TSH reference range as between 0.4 and 4.5 mU/L.

Subclinical Hypothyroidism

With that, if you have subclinical hypothyroidism, meaning your TSH is mildly elevated (let's say around 6.0 mU/L) and your thyroxine (T4) level is normal, the fact that you have positive TPO antibodies may influence your doctor into treating you with a low dose of thyroid hormone replacement medication.

Your doctor may be even more swayed to treat (or try it out) if you are having hypothyroid symptoms, like constipation, depression, or scalp hair loss.

The main reason behind initiating therapy is that treating subclinical hypothyroidism may prevent progression to overt hypothyroidism (when your TSH is elevated and your T4 level is low). 

Treatment may also improve symptoms or other signs of hypothyroidism (like high cholesterol).

Treating Subclinical Hypothyroidism: Other Factors to Keep in Mind 

In addition to the presence of TPO antibodies and whether you have symptoms, your doctor will consider other factors when deciding whether or not to treat subclinical hypothyroidism:

Age

One factor is age—TSH levels may rise with increasing age, even in people without thyroid disease.

This is why a doctor may prescribe thyroid hormone replacement medication for a younger person with a mildly elevated TSH, normal T4, and positive TPO antibodies, but not for an older person (over the age of 60) with the same blood test results; although, a "watch and wait" approach is often taken, meaning you will have your TSH periodically checked to see if it rises.

Other Health Problems

Having a family history of thyroid disease or a personal history of high cholesterol may further sway a doctor into treating subclinical hypothyroidism.

Pregnancy

Since subclinical hypothyroidism may increase the risk of miscarriage and premature birth, treatment is generally started.

Downsides to Treating Subclinical Hypothyroidism

While thyroid hormone replacement medication is generally well-tolerated, there are some potential downsides to initiating treatment for subclinical hypothyroidism.

One major concern is the risk of overtreatment, meaning a person becomes hyperthyroid, which can put them at risk of developing atrial fibrillation and osteoporosis.

Other potential downsides include cost, inconvenience, and the "medicalization" of a normal condition.

A Word from Verywell 

If you or a loved one has subclinical hypothyroidism, also having positive TPO antibodies (Hashimoto's disease) may sway your doctor into initiating a trial of levothyroxine.

In the end, deciding whether or not to start thyroid treatment requires a thoughtful discussion with your personal physician—and remember, what is right for your thyroid and overall health may not be right for someone else. 

Sources: 

Burns RB, Bates CK, Hartzband P, Smetana GW. Should we treat for subclinical hypothyroidism?: Grand Rounds Discussion from Beth Israel Deaconess Medical Center. Ann Intern Med. 2016 Jun 7;164(11):764-70.

Garber, J, Cobin, R, Gharib, H, et. al. "Clinical Practice Guidelines for Hypothyroidism in Adults: Cosponsored by the American Association of Clinical Endocrinologists and the American Thyroid Association." Endocrine Practice. Vol 18 No. 6 November/December 2012.

Jonklaas J 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):1670-1751.

Reid SM, Middleton P, Cossich MC, Crowther CA, Bain E. Interventions for clinical and subclinical hypothyroidism pre-pregnancy and during pregnancy. Cochrane Database Syst Rev. 2013 May 31;(5):CD007752.

Thangarantinam S, Tan A, Knox E, Kilby MD, Franklyn J, Coomarasamy A. Association between thyroid autoantibodies and miscarriage and preterm birth: meta-analysis of evidence. BMJ. 2011 May 9;342:d2616.