Hypothyroidism, or an underactive thyroid, is when the thyroid gland produces too few hormones. Low levels of thyroid hormones can cause a wide range of signs and symptoms, from changes in mental functioning to digestive issues.

The thyroid is a butterfly-shaped gland that sits in front of the neck. Thyroid hormones play a vital role in regulating metabolism and energy use and affect almost all of the body’s organs.

In this article, we describe 12 common signs and symptoms of hypothyroidism. We also discuss the later symptoms of untreated hypothyroidism, how common hypothyroidism is, and when to see a doctor.

Infographic showing the effects of hypothyroidism on the body. Share on Pinterest
Image credit: Stephen Kelly, 2019

Fatigue is one of the most common symptoms of hypothyroidism.

Many people with the condition report feeling so exhausted that they are unable to go about their day as usual.

The fatigue occurs regardless of how much sleep a person gets or how many daytime naps they take. Treatment for hypothyroidism usually improves people’s energy levels and functioning.

Thyroid hormones help to regulate body weight, food intake, and the metabolism of fat and sugar. People with low levels of thyroid hormones can experience weight gain and an increase in body mass index (BMI).

Even mild cases of hypothyroidism may increase the risk of weight gain and obesity. People with the condition often report having a puffy face as well as excess weight around the stomach or other areas of the body.

Hypothyroidism can affect a person’s muscles and joints in numerous ways, causing:

  • aches
  • pains
  • stiffness
  • swelling of the joints
  • tenderness
  • weakness

Research also suggests a link between thyroid disorders and rheumatoid arthritis, which is an autoimmune condition that causes painful swelling in the lining of the joints. Effective treatment for both conditions will help people manage their symptoms.

It is common for individuals with untreated hypothyroidism to experience:

  • anxiety
  • depression
  • apathy, or general lack of interest or feelings of indifference
  • impaired memory function
  • less attentiveness and concentration
  • low moods
  • slower thinking and speech

These symptoms can occur because the brain requires thyroid hormones to function correctly. Research shows that low levels of thyroid hormones can cause changes in brain structure and functioning.

These brain changes can reverse once a person begins treatment.

Hypothyroidism can slow down metabolism, leading to a drop in core body temperature. As such, some people with low levels of thyroid hormones may feel cold all the time or have a low tolerance to the cold.

This feeling of coldness can persist, even when in a warm room or during the summer months. People with hypothyroidism often report having cold hands or feet, although they may feel their whole body is cold.

These symptoms are not exclusive to hypothyroidism, however. Circulation problems or anemia can also cause people to feel chilly.

Digestion is another body function that can slow down due to hypothyroidism.

Studies report that an underactive thyroid can cause problems with movement through the gut and the activity of the stomach, small intestine, and colon.

These digestive changes cause some people to experience constipation.

Doctors typically define constipation as having fewer than three bowel movements a week. A person may also have hard stools, difficulty passing stool, or a feeling of being unable to empty the rectum fully.

Thyroid hormones play a vital role in removing excess cholesterol from the body via the liver. Low hormone levels mean that the liver struggles to carry out this function and blood cholesterol levels can increase.

Research suggests that up to 13 percent of individuals with high cholesterol also have an underactive thyroid. As a result, many experts recommend that doctors routinely test people with high cholesterol for hypothyroidism.

Treating the thyroid problem may help reduce cholesterol levels, even in those who do not take cholesterol-lowering drugs.

People with hypothyroidism may also have a slower heart rate, or bradycardia. Low thyroid levels can affect the heart in other ways too. These effects may include:

  • changes in blood pressure
  • variations in heart rhythm
  • less elastic arteries

Bradycardia can cause weakness, dizziness, and breathing problems. Without treatment, this heart condition may result in serious complications, such as high or low blood pressure or heart failure.

Untreated hormone disorders, including thyroid problems, can contribute to hair loss. This is because thyroid hormones are essential for the growth and health of hair follicles. Hypothyroidism may cause hair loss from the:

  • scalp
  • eyebrows
  • legs
  • other body parts

People with thyroid problems are also more prone to developing alopecia, which is an autoimmune condition that causes hair to fall out in patches.

An underactive thyroid affects the skin in various ways and can cause symptoms, such as:

  • dry, coarse skin
  • paleness
  • thin, scaly skin

People with hypothyroidism may also develop dry, brittle, and coarse hair or dull, thin nails that break easily.

These symptoms usually clear up once people begin thyroid hormone therapy.

A goiter is an enlargement of the thyroid gland that appears as a swelling at the base of the neck. Other goiter symptoms include:

  • a cough
  • hoarseness
  • problems swallowing and breathing

Many thyroid problems can result in a goiter, including Hashimoto’s thyroiditis, which is an autoimmune condition that damages the thyroid gland, stopping it producing enough hormones.

Other causes include underactive thyroid and, less commonly in the United States, iodine deficiency.

People with an underactive thyroid may experience heavy or irregular menstrual periods or spotting between periods.

According to the Society of Menstrual Cycle Research, hypothyroidism causes these problems because it affects other hormones that play a role in menstruation, such as by:

  • impairing the degradation of estrogen
  • reducing the amount of sex hormone-binding globulin

Hypothyroidism develops slowly and symptoms may go unnoticed for a long time. In the event that hypothyroidism is left untreated, a person may develop the following late symptoms:

According to the National Institute of Diabetes and Digestive and Kidney Diseases, hypothyroidism affects around 4.6 percent of people aged 12 years or older in the U.S. However, most of these individuals experience only mild symptoms.

Hypothyroidism is more likely to occur in women and people over 60 years of age.

Other risk factors include:

  • a personal or family history of thyroid problems
  • previous thyroid surgery or radiation treatment to the neck or chest
  • having been pregnant recently
  • other health conditions, such as Turner syndrome, Sjögren’s syndrome, or certain autoimmune conditions

It is vital for people with unexplained fatigue or other signs or symptoms of hypothyroidism to see a doctor. Without treatment, an underactive thyroid can lead to serious complications, such as infertility, obesity, and heart disease.

A doctor can carry out a simple blood test to check a person’s thyroid hormone levels. Treatment for hypothyroidism involves taking synthetic thyroid hormones. These medications are safe and effective once a person takes the right dose.

Below are some commonly asked questions about hypothyroidism.

What are the warning signs of hypothyroidism?

Warning signs of hypothyroidism may include tiredness, cold intolerance, weight gain, change in voice, and dry skin. However, it can present differently according to the age and sex of a person (among other factors).

What are the 10 major clinical symptoms of hypothyroidism?

Hypothyroidism may manifest in the following ten signs: fatigue, excessive somnolence, increased cold sensitivity, pale and dry skin, face puffiness, hoarse voice, unexplained weight gain, muscle weakness, and depression.

What age does hypothyroidism usually start?

Hypothyroidism can start at any age. However, it is more likely to occur in people over 60.

How does hypothyroidism affect the hands?

Hypothyroidism can affect all parts of the body, including the hands. This can lead to:

  • cold hands
  • pain, numbness, and tingling sensations in the hand
  • brittle fingernails
  • white ridges on the nails
  • nail splitting
  • slow fingernail growth

Hypothyroidism (underactive thyroid) is a relatively common condition, affecting almost 5 people out of 100 in the U.S. This condition occurs when the thyroid gland does not produce enough hormones.

Because thyroid hormones are essential for the normal functioning of many different parts of the body, low levels can cause a wide variety of symptoms.

This includes fatigue, weight gain, and memory and mood changes.

It is vital that people with these symptoms or other symptoms of hypothyroidism see their doctor for evaluation and treatment. Doctors can prescribe hormone replacement pills to treat individuals with low levels of thyroid hormones effectively.

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