Hypothyroidism: Symptoms, Causes & Treatment Options

Updated in April 2023

Hypothyroidism is characterized by low thyroid activity in which fewer T3 and T4 hormones are produced. It is one of the most common endocrine conditions and is associated with symptoms like fatigue, decreased heart rate, weight gain, hair loss, and dry skin.

This condition is more common in women over 40 years old who have close relatives with hypothyroidism. It is also common in people who have had a part of or the whole thyroid removed, or those who have had some kind of radiation treatment to the head and neck.

Treatment for hypothyroidism is aimed at regulating thyroid hormone levels and thus relieving the symptoms. For this, endocrinologists usually prescribe synthetic hormones such as levothyroxine. 

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Signs and symptoms 

Signs and symptoms associated with an underactive thyroid can appear gradually through the years. The lower the T3 and T4 hormone levels, the more prevalent the symptoms will be. The major signs and symptoms of hypothyroidism include:

  • Headache, muscle, and joint pain;
  • Irregular menstruation, which can cause trouble conceiving;
  • Fragile, breakable nails and dry, rough skin;
  • Swollen eyelids;
  • Hair loss and finer, dry, dull hair;
  • Slower heartbeat;
  • Constant fatigue;
  • Difficulty concentrating, and memory problems;
  • Low sex drive;
  • Increase in weight with no apparent cause.

In addition, there are cases where the person may undergo personality changes, depression, and dementia, however, these symptoms only happen with severely low levels of T3 and T4.

Hypothyroidism in children can also interfere with development. When experienced during adolescence, puberty may come later and the child may not grow as much. In addition, if a baby has congenital hypothyroidism, and it is not detected in the first week after birth, the child may show signs of neurological problems.

Complete our online symptom checker if you think you may have symptoms of a thyroid issue to assess your risk.

Main causes

The most common cause of hypothyroidism is Hashimoto's thyroiditis, which is an autoimmune disease where the body's antibodies mistakenly attack the thyroid gland. Hypothyroidism can also occur due to an iodine deficiency, otherwise known as goiter. This condition is characterized by an increase in thyroid size but a decrease in T3 and T4 production, due to low iodine concentration.

Treatment for hyperthyroidism (overactive thyroid) or the use of some types of medications such as lithium carbonate, amiodarone, propylthiouracil, or methimazole can also lead to hypothyroidism. Therefore, you should consult and t to visit an endocrinologist if any of these symptoms appear after starting any new drugs.

Some people may choose to supplement with thyroid hormones with the aim of weight loss. However, this is not recommended as this increases your risk for developing hypothyroidism, as the body will stop naturally producing thyroid hormones.

In addition to these causes, hypothyroidism can also happen during pregnancy or in the postnatal stage, however it usually resolves in the postpartum stage. 


The best way to diagnose hypothyroidism is to consult an endocrinologist. The doctor will evaluate the presenting signs and symptoms and order a blood test that checks for T3 and T4 levels. With hypothyroidism, T3 and T4 will be low, while TSH levels will be elevated.

In addition, the doctor may also order antibody tests, lymph node mapping and thyroid ultrasound. Learn more about the different thyroid tests your doctor may order to confirm a diagnosis.

When to do a thyroid blood test

If you have clear signs and symptoms of hypothyroidism or if you fall into one of the categories below, a thyroid blood test may be recommended: 

If you are a woman over 50 years old  If you have had radiation therapy on the head or neck If you have type 1 diabetes 
If you are pregnant If you've done thyroid surgery  If you have auto-immune diseases
If you have goiter  If you have a family history of thyroid conditions If you have heart conditions
If you have Down Syndrome  If you have Turner Syndrome  If you're lactating and you're not pregnant or breastfeeding 

Treatment options

Treatment for hypothyroidism is relatively simple and consists of hormonal replacement with synthetic hormones like levothyroxine. Levothyroxine should be taken when fasting, at least 30 minutes before breakfast, so that the food digestion does not decrease its effectiveness. An endocrinologist should prescribe the dose, which can vary depending on circulating T3 and T4 levels.

After 6 weeks of medication, the doctor may re-evaluate your symptoms and order another thyroid blood test  to check whether you need to adjust the dose until the free T4 levels are normal. After that thyroid tests should be carried out once or twice a year, to check whether the medication doses need adjusting.

In addition to medication, it's important to manage blood cholesterol levels by avoid eating fat, and adhering to a diet that promotes optimal liver functioning. Intense stress can also interfere with the secretion of thyroid hormones. In some cases, a consult with a registered dietitian can be helpful as they can recommended certain foods and iodine supplements which can help to reduce the symptoms associated with hypothyroidism.

Subclinical hypothyroidism is diagnosed in people with low T3 and T4 levels but present with no symptoms. The doctor may still opt to prescribe medication to help decrease the risk of cardiovascular problems. This is especially important for people who are already overweight or have high cholesterol or diabetes.