What is Subclinical Hypothyroidism?

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  • Written By: wiseGEEK Writer
  • Edited By: O. Wallace
  • Last Modified Date: 01 August 2019
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Subclinical hypothyroidism relates to unusual findings in blood tests of thyroid function. In this condition, people usually have normal blood levels of the thyroid hormones T3 and T4. At the same time, blood analysis of thyroid-stimulating hormone (TSH) is elevated to high normal or above normal levels. This finding is potentially an indication that a person will begin to produce lower T3 or T4 in the next few years, but there is considerable dispute on whether to respond to these laboratory results with treatment.

Poor thyroid function is still not fully understood, but continued studies suggest a great deal about how vital it is to have the right thyroid levels. There are some endocrinologists who advocate for treating hypothyroidism if TSH is too high or if T3 or T4 persistently test in low-normal ranges. A number of debates exist on the right range, and over time, many different ranges have been suggested as more appropriate than the ones now used by laboratories. There is certainly an association between poorly functioning thyroid and conditions like depression, anxiety and bipolar disorder, and other studies suggest the importance of treating conditions like subclinical hypothyroidism if people suffer from high serum cholesterol levels or if they show any symptoms of poor thyroid function like difficulty losing weight, high sensitivity to temperature, especially cold, or persistent fatigue.


It’s also important that subclinical hypothyroidism be differentiated from other types of thyroid illness. Normal T4 and T3 levels might present with high TSH levels and high antibodies for TSH. The presence of these antibodies suggests a condition called Hashimoto’s thyroiditis, a relatively common cause of thyroid disorders. It does require immediate treatment.

Doctors may approach treatment guidelines in different ways, but the actual treatment for subclinical hypothyroidism tends to be the same. Replacement for T4, called levothyroxine (Synthroid®) is given so that the thyroid-stimulating hormone isn’t needed in as great a supply. Treatment should result in TSH levels dropping. Again, doctors can have preference in determining the best medicine. Levothyroxine is notoriously unstable and may vary by manufacturer and some physicians feel that the non-generic version of the drug, Synthroid®, is more reliable.

The other approach to subclinical hypothyroidism is not to treat it, or at the least not to treat it initially. Sometimes a repeat blood test done a few months later will show normal TSH levels. Doctors lean more toward prescribing medicine right away if the patient has several symptoms of hypothyroidism, a family history of the illness, symptoms of depression, additional autoimmune disorders, high blood cholesterol levels, heart disease, or any illnesses or exposure that might suggest the thyroid gland is compromised. At minimum, repeat tests should be done for several years to watch for decreased levels of T4 or further elevation of TSH.



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