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Understanding TSH Suppression for Hypothyroidism

Learn about TSH suppression and the effects it can have on your overall health and thyroid.
Understanding TSH Suppression for Hypothyroidism
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When you think of hypothyroidism, you usually think of low levels of thyroid hormones like thyroxine (T4) and triiodothyronine (T3). But, another hormone plays a crucial role in regulating the production and secretion of your thyroid hormone: thyroid-stimulating hormone (TSH). 

When the pituitary gland releases TSH, it tells your thyroid to make and release thyroid hormone. As thyroid hormone levels increase, your pituitary gland slows down and stops releasing TSH. Thyroid hormone levels decline as your cells use this hormone. The decline signals your pituitary gland to release more TSH, and the cycle continues.

People with an underactive thyroid typically have high TSH levels with low T4 and T3 levels. In hypothyroidism, the pituitary gland tries to stimulate your thyroid to make thyroid hormones by releasing more and more TSH. But for various reasons, it can’t.

When your TSH is below the low end of the reference range – or TSH is undetectable – due to medication, this is called “TSH suppression.”  It’s somewhat common for patients with hypothyroidism to have suppressed TSH levels, as in some people, it helps with symptom management. Yet, there are risks associated with too low a TSH level. Ahead, we discuss TSH suppression and its implications on thyroid disease and your health. 

What is TSH suppression?

The American Thyroid Association hypothyroidism guidelines consider a normal TSH range as 0.4–4.0 mIU/L. There is controversy about adjusting this range based on age, with a more lenient range for older adults. But that is a story for another day!

Suppression is defined as a level below the reference range, and there are several different levels of TSH suppression:

  • Mild suppression: 0.1 to 0.5 mU/L
  • Moderate suppression: 0.1 to 0.01 mU/L
  • Severe suppression: below 0.01 mU/L

The duration and extent of TSH suppression depend on the goal. 

How is TSH suppressed?

High doses of thyroid hormone replacement medication, like levothyroxine or natural desiccated thyroid (NDT), will suppress your TSH production.

Levothyroxine is a synthetic version of thyroxine (T4). NDT is a natural drug containing T4 and the active thyroid hormone triiodothyronine (T3). When you take these medications, thyroid levels in your blood increase, signaling your pituitary gland to stop releasing TSH.

Over time and with consistent dosing, your TSH level will drop. Increasing your thyroid hormone replacement medication dose will further reduce your TSH level. Most people with moderate to severely suppressed TSH levels take higher doses of thyroid medication. 

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Who benefits from TSH suppression?

Two groups can benefit from TSH suppression: those with thyroid cancer or hypothyroidism.

Thyroid cancer patient

TSH suppression may help prevent thyroid cancer recurrence or stem the growth of thyroid nodules. According to guidelines, there are two situations where TSH suppression is recommended.

  • Those with an active tumor
  • Those with a very aggressive form of thyroid cancer, despite radioactive iodine and surgery

In these situations, doctors target a moderately suppressed initial TSH level of less than 0.1 mU/L. This goal can change over time based on other risk factors.

For low-risk thyroid cancer patients, guidelines recommend aiming for a TSH level around 0.1–0.5 mU/L. Going lower may increase risks associated with TSH suppression without gaining more benefits.

Hypothyroid patients

Regardless of the cause, patients with hypothyroidism are commonly prescribed thyroid hormone replacement drugs to help manage thyroid hormone levels. Since these drugs replace your natural thyroid production, it signals the pituitary gland to stop producing TSH.

As your TSH levels decrease and thyroid hormone levels increase, signs and symptoms of hypothyroidism should resolve. But, if your TSH drops too low, your risk of adverse effects increases.

What are the risks of TSH suppression?

Suppressing your TSH too much can have negative consequences on your health. Some describe this situation as “subclinical thyrotoxicosis,” a mild form of hyperthyroidism.

At normal range TSH levels, bones are protected. TSH-suppressive therapy, however, may lead to bone loss, causing an increased risk of

Post-menopausal women are at a higher risk of fracture and bone-related complications associated with TSH suppression compared to men and pre-menopausal women. Post-menopausal women currently on or starting TSH suppression therapy are at a higher risk of osteoporosis and should have their bone density checked yearly. If needed, your healthcare provider can prescribe anti-reabsorption therapy such as Fosamax, Reclast, or Actonel to help prevent bone loss.

TSH suppression can also affect your heart. High thyroid hormone levels may stimulate the muscles in your heart, changing how it functions.

A 2022 review showed those on TSH-suppressing doses of thyroid hormone replacement drugs after thyroid surgery had an increased risk of cardiovascular disease, specifically atrial fibrillation. In this condition, your heart rhythm is irregular. Also, those receiving TSH suppression had faster heartbeats and higher blood pressure than those not undergoing TSH suppression.

Apart from the effects on your bones and heart, other symptoms caused by suppressed low TSH include

A note from Paloma Health

As discussed, TSH suppression is a natural consequence of taking higher doses of thyroid hormone replacement medication. However, suppressions put you at a greater risk of developing signs and symptoms of subclinical thyrotoxicosis.

If you are wondering if your hypothyroidism treatment regimen is right for you, schedule a free, no-obligation appointment with our care managers. We have a team of thyroid specialists that take a personalized approach to managing your hypothyroidism.

Also, please note that while TSH suppression is commonly used to treat thyroid cancer, our thyroid providers do not see patients with a history of thyroid cancer.

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Jonklaas J, Bianco AC, Bauer AJ, et al. Guidelines for the Treatment of Hypothyroidism: Prepared by the American Thyroid Association Task Force on Thyroid Hormone Replacement. Thyroid. 2014;24(12):1670-1751. doi:

Brancatella A, Marcocci C. TSH suppressive therapy and bone. Endocr Connect. 2020 Jul;9(7):R158-R172. doi:

Thyroid Stimulating Hormone (TSH) Suppression | ThyCa: Thyroid Cancer Survivors’ Association, Inc. Accessed June 19, 2023.

Sharma, V. What are the TSH targets for patients with thyroid cancer? American Thyroid Association. 2021;14(12):13-14. Accessed June 19, 2023.

Hannoush ZC, Weiss RE. Thyroid Hormone Replacement in Patients Following Thyroidectomy for Thyroid Cancer. Rambam Maimonides Med J. 2016;7(1):e0002. doi:

Yang X, Guo N, Gao X, Liang J, Fan X, Zhao Y. Meta-analysis of TSH suppression therapy and the risk of cardiovascular events after thyroid cancer surgery. Front Endocrinol (Lausanne). 2022;13:991876. doi:

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Emilie White, PharmD

Clinical Pharmacist and Medical Blogger

Emilie White, PharmD is a clinical pharmacist with over a decade of providing direct patient care to those hospitalized. She received her Doctor of Pharmacy degree from Massachusetts College of Pharmacy and Health Sciences. After graduation, Emilie completed a postgraduate pharmacy residency at Bon Secours Memorial Regional Medical Center in Virginia. Her background includes caring for critical care, internal medicine, and surgical patients.

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