An Overview of Hypothyroidism

Hypothyroidism means that you do not have enough–or even any–thyroid hormone. It is sometimes also referred to as an "underactive" or "slow" thyroid.

When functioning normally, your thyroid—a small, butterfly-shaped gland in your neck—uses dietary iodine to produce thyroid hormone. The purpose of thyroid hormone is to regulate how your organs, glands, tissues, and cells use oxygen and energy. The human body needs thyroid hormone in order to survive and function.

When you don’t have a working thyroid, or your thyroid is unable to produce enough hormone, the result is the condition known as hypothyroidism.

The thyroid, located just above the collarbone.

What Causes Hypothyroidism?

There are a number of health issues and conditions that result in a thyroid that can’t produce enough—or any—thyroid hormone.

Autoimmune/Hashimoto’s Thyroiditis
The autoimmune disease Hashimoto’s thyroiditis is the most common cause of hypothyroidism in the United States.

In this case, antibodies attack the thyroid gland, making it incapable of functioning properly. Eventually, the thyroid can become atrophied and/or incapable of producing thyroid hormone. In some cases, the underlying trigger of autoimmunity may be reversible, resolving the hypothyroidism. In other cases, the destruction of the thyroid gland—and an inability to produce enough thyroid hormone—is permanent.

Post-Surgical Hypothyroidism
Post-surgical hypothyroidism refers to insufficient thyroid hormone due to surgical removal of all or part of the thyroid gland. Surgery on the thyroid is known as a thyroidectomy.

Partial or full thyroidectomy is a treatment sometimes used for goiter, nodules, Graves’ disease, and hyperthyroidism, and is frequently a part of thyroid cancer treatment.

Post-Ablation Hypothyroidism
Radioactive iodine (RAI) is treatment used for thyroid cancer, Graves’ disease, hyperthyroidism, and in some cases, to treat toxic nodules. After RAI treatment, the thyroid’s ability to produce thyroid hormone can be impaired or completely destroyed, resulting in a deficiency or total lack of thyroid hormone.

Post-Radiation Hypothyroidism
Exposure to radiation treatments to the head and neck, or radioactive fallout from nuclear accidents like Chernobyl or Fukushima, are risk factors for the development of hypothyroidism.

Congenital Hypothyroidism
Some newborns come into the world without a thyroid gland, meaning they do not have the ability to produce thyroid hormone. In some cases, the gland is malfunctioning or malformed in some way and is not capable of producing enough thyroid hormone.

Iodine-Deficiency Hypothyroidism
Iodine is the building block of thyroid hormone, and sufficient levels of iodine intake are essential for you to produce thyroid hormone.

Some areas of the country and the world were originally covered by the ocean and, as a result, tend to have more iodine in the soil, which ends up in the food supplies in those areas. But there are areas that were never covered by ocean and have low iodine levels in their soil. (The so-called "Goiter Belt" area around the Great Lakes in the United States is an example.)

Some iodine-deficient areas have helped resolve the issue by adding iodine to salt. But there are many areas in the world that are significantly iodine-deficient and don’t have iodization programs, resulting in high rates of iodine deficiency and higher risks of thyroid problems. Iodine deficiency is particularly dangerous in pregnant women; the resulting lack of thyroid hormone can result in a range of disabilities in their children. In some areas of the world, there is a much high rate of cretinism, a condition that causes serious mental retardation and other disabilities in the children of iodine-deficient mothers. Iodine deficiency is considered the leading preventable cause of mental retardation in the world.

Drug-Induced Hypothyroidism
There are certain medications that have the ability to cause hypothyroidism. While this is not a comprehensive list, some of the more commonly known medications include:

  • Antithyroid drugs, including propylthiouracil (PTU) and methimazole
  • Lithium
  • Amiodarone
  • Interferon
  • Interleukin-2
  • Glucocorticoids/steroid drugs
  • Metformin

In some cases, high-dose supplementation with potassium iodide and iodine, or iodine-rich herbs like kelp or bladderwrack, can result in hypothyroidism in some people.

Goitrogen-Induced Hypothyroidism
Very high consumption of raw goitrogens–foods that have chemicals in them that slow the thyroid–can be a cause of hypothyroidism. Goitrogens include soy, cruciferous vegetables, and a number of other foods.

Secondary/Central Hypothyroidism
Secondary or central hypothyroidism is a result a defect in the functioning/communications of the pituitary gland and the hypothalamus.

Traumatic Hypothyroidism
Serious trauma to the neck, such as whiplash or breaking your neck, has been linked to the onset of hypothyroidism in some people.

Hypothyroidism of Unknown Origin/Idiopathic Hypothyroidism
There are cases where the thyroid becomes underactive and no other underlying causes or diseases have been identified.

What Are the Risk Factors for Hypothyroidism?

There are a number of risk factors for hypothyroidism, but gender could be considered the most important. Being a woman means you are eight to 10 times more likely than a man to develop a thyroid condition. And while women are at a much higher risk of hypothyroidism than men, there are some additional points when that risk is even greater for women, including:

  • Puberty
  • Current pregnancy
  • Recent childbirth (within a year)
  • Perimenopause
  • Menopause

Thyroid History: If you have family members who had or have thyroid disease, this increases your risk of hypothyroidism. Also, if you have a history of past thyroid issues, or have had specific thyroid treatments such as radioactive iodine (RAI) or thyroid surgery, this can is a risk for hypothyroidism.

Autoimmune History: If you or family members have other autoimmune diseases—even if they are not autoimmune thyroid diseases like Graves’ disease and Hashimoto’s thyroiditis—you are at more risk of developing hypothyroidism.

Other risk factors include the following:

  • Iodine deficiency or excess: You are in an iodine-deficient area and not supplementing with iodine, or you are being exposed to excessive amounts of iodine due to supplementation, for example.
  • Past or current cigarette smoking
  • Medications: Taking certain medications, like lithium or the heart medication amiodarone, increase your risk of hypothyroidism.
  • Exposure to radioactivity or radioactive fallout
  • Overconsumption of soy and raw goitrogenic foods
  • Recent surgery or trauma to the neck area, which is linked to some cases of thyroid dysfunction
  • Hypopituitarism (an underfunctioning pituitary gland) is a risk for hypothyroidism. Hypopituitarism can be caused head injuries; infections in or surgery to the brain; stroke; benign or malignant tumors in the brain or pituitary gland; severe hemorrhage during childbirth (which damages the pituitary, known as Sheehan syndrome); and congenital genetic mutations, among other causes.

What Are the Signs and Symptoms of Hypothyroidism?

There are some observable signs of hypothyroidism that can be measured, detected, or identified in a clinical examination with your practitioner. These signs of hypothyroidism include:

  • An enlarged neck
  • Palpable enlargement in the thyroid gland
  • A visible or palpable lump in the neck
  • An unusually low pulse or blood pressure
  • Slow or sluggish reflexes
  • Puffiness in the face, especially around the eyes
  • Puffiness or swelling of the hands and feet (known as edema)
  • Hair loss, especially the loss of hair in the outer edge of the eyebrow
  • High cholesterol levels that are unresponsive to cholesterol-lowering medication
  • Chronic or severe constipation
  • Lower-than-normal body temperature

There are some hypothyroidism signs that are unique to women:

  • You have severe menstrual cramps
  • You have a history of irregular menstrual cycles
  • You are having difficult perimenopausal or menopausal symptoms
  • You have had trouble conceiving a baby
  • You have a history of failed assisted reproduction treatments
  • You have a history of recurrent miscarriage
  • You had postpartum depression in the past, or are experiencing it now
  • You had difficulty breastfeeding in the past, or are experiencing it now

Some other common hypothyroidism symptoms you may experience include:

  • You feel fatigued, rundown, sluggish, and exhausted, even after a lengthy sleep
  • You feel depressed or blue, or feelings of sadness or worthlessness
  • You are unexpectedly gaining weight, despite no change to your healthy diet and exercise
  • You are unable to lose weight, or you may even gain weight on a reduced-calorie, healthy diet with increased exercise
  • You feel anxious or restless
  • Your moods change easily
  • You have “brain fog,” difficulty concentrating, and difficulty remembering
  • You feel cold when others feel hot
  • Your hair is coarse and dry, breaking, brittle, or falling out
  • Your skin is coarse, dry, scaly, and thick, especially the soles of your feet
  • You have a hoarse or gravelly voice
  • You have aches and pains in joints, hands, and feet, especially frozen shoulder, carpal tunnel syndrome, tarsal tunnel syndrome, or plantars fasciitis
  • You have no sex drive
  • You’re snoring more lately, or you have developed sleep apnea
  • Your eyes feel gritty, dry, and sensitive to light
  • Your neck or throat feels different, and you don’t want to wear restrictive items like ties or turtlenecks

Some specialized signs of hypothyroidism in newborns include: 

  • Low muscle tone
  • Poor feeding
  • Hoarse crying

Some specialized signs of hypothyroidism in children and adolescents include: 

  • Growth retardation
  • Delayed skeletal maturation
  • Delayed puberty
  • Decreased energy
  • Appearing swollen or puffy
  • Weight gain without increased appetite
  • Decreased growth rate
  • Constipation or harder stools 
  • Deterioration in handwriting

How Is Hypothyroidism Diagnosed?

Hypothyroidism diagnosis typically is done by a combination of a clinical examination and blood tests.

A Clinical Examination
A clinical thyroid examination includes a manual and visual examination of the thyroid gland, and looks for the clinical signs of hypothyroidism that can be seen.

Blood Testing
The main blood test used to diagnose hypothyroidism is the thyroid stimulating hormone (TSH) test. This test measures TSH, a pituitary hormone. TSH rises when it detects low levels of thyroid hormone, and drops when it detects excess thyroid hormone. Laboratories have established a reference range, and levels above the reference range are considered potentially indicative of hypothyroidism.

At many labs, the reference range runs from around 0.5 to 5.0. Some endocrinologists and mainstream practitioners believe in diagnosing and treating hypothyroidism only if your TSH level is above 5.0. Others feel that levels between 5.0 and 10.0 are “subclinical hypothyroidism” and may not warrant treatment. Levels about 10.0 are considered overt hypothyroidism and are usually treated.

A subset of practitioners believes that levels that are in the high-normal area of the reference range, when accompanied by thyroid risk factors and symptoms, may warrant a trial of thyroid hormone replacement treatment for hypothyroidism. Given guidelines that say that pregnant women should have a TSH no higher than 2.5 during their first trimester, and 3.0 in the second and third trimesters, some—but not all—doctors diagnose and treat according to those guidelines.

NOTE: Since late 2002, the American Association of Clinical Endocrinologists (AACE) and other professional groups have gone back and forth regarding recommendations to narrow the TSH range and making the top end of the reference range around a TSH level of 3.0.

In some cases, the unbound and available levels of the actual circulating thyroid hormones—free thyroxine (free T4) and free triiodothyronine (free T3)—are measured. There are reference ranges for these two hormone tests, and levels below the reference range (showing that there is insufficient free T4 and/or free T3) are considered indicative of hypothyroidism.

Because most cases of hypothyroidism in the United States are caused by Hashimoto’s disease, some practitioners also test thyroid peroxidase antibodies (TPO Ab). Elevated levels of these antibodies outside of the normal range can confirm that the hypothyroidism is caused by autoimmune Hashimoto’s disease. A subset of conventional practitioners treat patients with hypothyroidism symptoms and elevated TPO Ab, even when TSH, free T4, and free T3 are within the reference range, as there is evidence that this treatment may lower antibodies and prevent progression to overt hypothyroidism.

Many integrative practitioners have a different view of diagnosis and treatment, and in addition to history and clinical examination, take the following view of diagnostic testing:

  • TSH should be in the lower end of the reference range
  • Free T4 and free T3 should be in the upper end of the reference range
  • Elevated TPO Ab should be tested to establish degree of autoimmunity
  • Reverse T3—a measurement of inactive T3—should be done . If elevated, it may further confirm hypothyroidism in the presence of symptoms even while other thyroid test levels fall within the reference range.

Remember, it’s never enough for your doctor to say, “your thyroid tests were fine.” You need to see the actual numbers yourself, to determine the actual levels, and understand how to interpret what those levels mean in terms of diagnosis and treatment.

How Is Hypothyroidism Treated?

Hypothyroidism is treated with thyroid hormone replacement drugs. These are prescription medications that replace the missing thyroid hormone in the body.

The most commonly prescribed thyroid hormone replacement drug is known generically as levothyroxine, a synthetic form of the thyroid hormone thyroxine (T4). Levothyroxine is sometimes referred to as l-thyroxine or l-T4. Well-known brand names include Synthroid, Levoxyl, and Unithroid, which are all levothyroxine in a tablet form. Tirosint is a liquid, gelcap, hypoallergenic formula of levothyroxine specifically created for people with digestive/absorption issues and allergies.

There is also a synthetic form of the T3 hormone, known as liothyronine. It is sometimes added to levothyroxine as part of a therapy known as T4/T3 combination treatment, though this practice is considered controversial by the many endocrinologists and mainstream practitioners. The only brand of liothyronine available in the United States is Cytomel. Some practitioners also prescribe time-released or sustained-release forms of liothyronine that are specially prepared by compounding pharmacies.

Natural Desiccated Thyroid
Finally, there is a hormone replacement drug called natural desiccated thyroid, sometimes abbreviated NDT or called "thyroid extract." A generic form of NDT is available, as are brand names in the United States, which include Armour Thyroid, Nature-throid, and WP Thyroid.

NDT was the first treatment for hypothyroidism and came onto the market more than 100 years ago. NDT is made from the desiccated (dried) thyroid glands of pigs, which is why it is also sometimes referred to as porcine thyroid.

NDT contains natural forms of both T4 and T3. While it has been available for more than a century, and is still in use today, it is considered controversial by the mainstream medical community and is prescribed more often by integrative, functional, and holistic physicians, as compared to endocrinologists and conventional physicians.

The official guidelines of various endocrinology organizations position levothyroxine as the preferred treatment, and discourage both T4/T3 combination therapy and use of NDT.

Integrative/Functional Approaches to Hypothyroidism

Integrative and functional medicine physicians have a different approach to treating hypothyroidism. They differ from conventional approaches in several key ways.

First, based on a growing body of research that shows that some patients don’t convert T4 to T3 effectively, they tend to routinely include free T4 and free T3 testing along with the TSH test. Many also routinely test for thyroid antibodies to identify the presence of an autoimmune disease, and measure reverse T3 to determine if this inactive hormone is contributing to worsening hypothyroidism.

Next, also based on a growing body of research that has shown that patients feel better, and have better resolution of symptoms on treatments that include both T4 and T3, they tend to favor T4/T3 therapy and NDT, and routinely include them as treatment options, along with levothyroxine-only treatment.

Finally, many of these practitioners also look for a root cause of the hypothyroidism, including celiac disease, which can trigger Hashimoto’s disease and hypothyroidism, iodine deficiency or excess, and nutritional deficiencies, among other factors. They then recommend treatments that may reverse these root causes, lower antibodies or—in some cases—resolve hypothyroidism. These include a gluten-free diet, an anti-inflammatory diet, and supplementation with iodine, tyrosine, selenium, and other nutrients, among other approaches.

How to Lose Weight Despite Hypothyroidism

One of the biggest complaints you may have as someone with hypothyroidism is the rapid onset of weight gain or a total inability to lose weight despite a rigorous diet and exercise program. Your doctor may downplay the link between your thyroid and your weight challenges, but you’re not alone. If you find yourself frustrated with your difficulty losing weight, start by visiting our Thyroid Diet and Weight Loss Information Center.

If you are having a weight struggle, you will also want to learn more about the hormonal factors that may make weight loss more difficult for people with hypothyroidism, including the role of reverse T3 and leptin.

And like many others, you are probably asking an important question: What is the best diet for thyroid patients? (A hint: There's no magic pill or one miracle diet.) There are, however, some approaches to eating that seem to be more successful for thyroid patients. And to make your weight loss effort a success, start learning about these 30 ways to make your diet work.

Support and Information About Hypothyroidism

One of the key elements of being a successful thyroid patient is staying informed about your hypothyroidism. That means reading, following the latest research, and connecting with others who can share their successful advice. Check out our helpful reviews of other key thyroid sites.

Here at Verywell, you will also find a wealth of resources to help you stay informed about every facet of hypothyroidism. In particular, be sure to check out our dedicated sections on:

A Word From Verywell

It's important to be aware that there can be significant challenges to getting a proper hypothyroidism diagnosis. Be knowledgeable and prepared before you see your doctor to ensure that you get the best possible care. A good starting point is to review these seven questions to ask your doctor about hypothyroidism. You may also want to explore some of the newest research and findings that may change the way hypothyroidism is treated in the future. 

If you are already being treated for hypothyroidism but you still don't feel right, please know that you're not alone. Many thyroid patients complain: "Help! I'm hypothyroid and I still don't feel well!" You may be undertreated or poorly treated, you may need additional T3, or you may not be getting a proper dosage. For some ideas to help, take a look at these 15 ways to feel and live well with hypothyroidism.

Also, remember that it's not just about medication. It's also important to eat well, get enough rest, make time for exercise and play, and manage your stress (meditation, for example, can help). And even if you feel like you’re fighting an uphill battle with doctors, treatments, and debilitating hypothyroidism symptoms, don’t EVER give up. You will eventually find the answers that will help you live well and feel well.


Braverman, L, Cooper D. Werner & Ingbar's The Thyroid, 10th Edition. WLL/Wolters Kluwer; 2012.

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.

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