Before Surgery

Thyroid Health: Obesity & Bariatric Surgery

by Brenda Hoehn on Aug 24, 2023

Thyroid Health: Obesity & Bariatric Surgery

Thyroid Health: Obesity & Bariatric Surgery

The thyroid is a butterfly-shaped gland located in the front of your neck and below the voice box. It’s also one of six glands that create the endocrine system.

According to the EPA, “The endocrine system, made up of all the body’s different hormones, regulates all biological processes in the body from conception through adulthood and into old age.”

A 2017 article from Clinical Thyroidology for the Public observed that obesity and hypothyroidism (an underactive thyroid) tend to occur in tandem.

This blog will discuss the thyroid, its relationship with weight and obesity, and how bariatric surgery may benefit thyroid health.

Read on to learn more.

Thyroid Function & Thyroid Hormones

The thyroid regulates many bodily processes, including metabolism (how effectively the body uses energy).

A properly functioning thyroid constantly releases a steady level of thyroid hormones into the bloodstream.

The two main thyroid hormones are:

  1. Triiodothyronine (T3)
  2. Tetraiodothyronine (T4 or thyroxine)

Iodine, which is only attainable through one’s diet, is a crucial building block for these hormones.

Regulating T3 & T4

While all six glands in the endocrine system affect each other in different ways, the communication between the hypothalamus, pituitary, and thyroid glands, also known as the hypothalamus-pituitary-thyroid (HPT) axis, is paramount for thyroid hormone regulation.

When necessary, the hypothalamus creates the TSH-releasing hormone (TRH), signaling the pituitary gland to release the thyroid-stimulating hormone (TSH/thyrotropin).

The pituitary gland will release less TSH to lower thyroid hormone levels and more TSH to increase thyroid hormone levels.

The body changes thyroid hormone levels to:

  • Promote growth and brain development (in children),
  • Maintain a healthy body temperature (99-97 degrees Fahrenheit),
  • Support pregnancy,
  • And more.

However, certain health conditions can cause inefficient communication between the hypothalamus, pituitary, and thyroid, causing either unnecessarily high (hyperthyroidism) or low (hypothyroidism) T3 and T4 levels.


An underactive thyroid characterizes hypothyroidism. Low thyroid hormone levels can cause symptoms such as:

  • Fatigue,
  • Depression,
  • Weight gain,
  • And more.

Hypothyroidism typically only causes an individual to gain about 5-10 pounds, while rare cases of severe hypothyroidism can cause significant weight gain. The condition can also make losing weight difficult despite following a healthy diet and exercise routine.

Hypothyroidism Treatment

In some cases, hormone replacement therapy is necessary to resolve the symptoms and complications of hypothyroidism.

To replicate normal thyroid function, patients take levothyroxine, the biological equivalent of T4. It comes in tablet, gel capsule, and liquid forms.

A patient’s weight, age, and other medical conditions dictate the initial levothyroxine dose, and treatment requires regular monitoring from a doctor to allow for any changes to the dose when necessary.

Obesity & Hypothyroidism

Hypothyroidism has a 12% prevalence rate in morbidly obese patients. Medical professionals clinically define hypothyroidism as an increase in circulating TSH levels.

Some bariatric patients’ hypothyroidism results from many possible reasons unrelated to their weight.

However, it is crucial to note that a significant amount of medical research correlates an increase in weight with an increased risk of hypothyroidism.

But elevated TSH levels in obese patients may not always indicate an underactive thyroid.

A 2019 study concluded that, in many cases, adipose (fatty) tissue in obese patients is the cause of elevated TSH levels, not the other way around.

Valdes et al. studied the increase in TSH concerning obesity and found that obesity equated to significantly higher TSH values than the normal range. This increase resulted from the HPT axis compensating for the extra energy expenditure needed with obesity, not necessarily from an underactive thyroid.

Thus, the average TSH reference values doctors use to test non-obese patients for hypothyroidism should be altered for obese patients to accommodate the necessary elevated TSH associated with obesity.

With this information in mind, all bariatric surgeons should properly test their patients for an underactive thyroid before surgery, as a dysfunctional thyroid can drastically affect weight loss. Plus, most insurance companies consider these tests as prerequisites for a patient to receive coverage.

Bariatric Surgery & Thyroid Health

Research is still evolving; however, current studies strongly suggest that bariatric surgery does help improve thyroid health in those with hypothyroidism.

A review in the Journal of Clinical Medicine referenced many studies, most of which concluded that weight loss following bariatric surgery causes TSH values to decrease.

A 2021 analysis on hypothyroidism and levothyroxine treatment following bariatric surgery analyzed 28 studies (totaling 1,284 patients) with a preoperative hypothyroidism diagnosis.

The postoperative statistics provided insights into how the decreased TSH values impacted hypothyroidism and the need for postoperative thyroid hormone replacement therapy.

Overall, postoperatively, the analysis found:

  • A significant average decrease in TSH levels.
  • A significant decrease in levothyroxine doses for patients who still required hormone replacement therapy.
  • The majority of patients’ preoperative hypothyroidism resolved entirely.

Bariatric surgery significantly affects TSH levels and hypothyroidism in patients. For this reason, doctors should regularly monitor patients’ TSH and thyroid hormone levels for at least two years after surgery.

Hormone Replacement Therapy After Bariatric Surgery

According to the American Thyroid Association, about 18% of bariatric surgery patients will require thyroid hormone therapy (e.g., levothyroxine) after surgery. However, it remains unclear how to determine the initial levothyroxine doses for obese hypothyroid patients and how those doses may need to change as the patient loses weight.

Despite the ongoing debate, based on an analysis by Juiz-Valiña et al., the current recommendation for determining levothyroxine dosages is based on a patient’s ideal body weight (dose/kg of IBW).

Bariatric Patients & Thyroid Health Overview

The medical research we referenced in this blog outlines how excessive weight gain has adverse side effects on thyroid health.

Bariatric surgery is an effective tool for inducing significant weight loss. Recent research notes that this weight loss lowers TSH levels.

However, even as TSH levels drop, doctors must monitor their patient’s thyroid health regularly. For patients with hypothyroidism, this includes adjusting their levothyroxine dosage as their thyroid health improves.

ProCare Health

Patients with a preoperative hypothyroidism diagnosis should ask their doctors about the benefits of taking a thyroid supplement before or after bariatric surgery, even if hormone replacement therapy is no longer needed.

Ask your doctor about our ProCare Health | Thyroid + | Capsules. These supplements support thyroid function by:

  • Activating thyroid hormone receptors,
  • Providing vital iodine,
  • Increasing T3 and free T4 levels,
  • Reducing TSH levels within a normal range,
  • And so much more!

By supporting healthy thyroid function, you stimulate your metabolism, aiding in more efficient weight loss.

Plus, our Thyroid + Capsules easily fit into your supplement regimen, as they do not interfere with any of our bariatric multivitamins or calcium supplements. They only enhance micronutrient absorption!

For more information about ProCare Health products and to gain access to our educational resources, please visit