Primary Hyperthyroidism

Primary hyperthyroidism occurs when your thyroid gland itself produces too much thyroid hormone, speeding up your body’s metabolism and affecting nearly every organ system. This condition differs from secondary hyperthyroidism, where the problem starts in the pituitary gland.

Table of contents

• What Is Primary Hyperthyroidism?
• Main Causes of Primary Hyperthyroidism
• Symptoms
• Who Is at Risk?
• How Is It Diagnosed?
• Treatment Options
• Potential Complications

What Is Primary Hyperthyroidism?

Primary hyperthyroidism is a condition where your thyroid gland makes too much thyroid hormone on its own^[1]. The thyroid is a small, butterfly-shaped gland located in the lower front of your neck^[5]. This gland produces hormones that control how your body uses energy—affecting your breathing, heart rate, weight, digestion, and moods^[6].

In primary hyperthyroidism, the problem begins within the thyroid gland itself, rather than being caused by another health issue^[8]. This is different from secondary hyperthyroidism, where the pituitary gland (a small gland at the base of your brain) sends out too much thyroid-stimulating hormone (TSH), which then tells your thyroid to produce excess thyroid hormone^[8].

When there is too much thyroid hormone in your body, your metabolism speeds up^[2]. This can throw your whole well-being off balance, making you feel unlike yourself or even out of control of your body^[2].

Main Causes of Primary Hyperthyroidism

Several conditions can cause your thyroid gland to become overactive. The three most common causes of primary hyperthyroidism are Graves disease, toxic multinodular goiter, and toxic adenoma^[4].

Graves’ disease is the most common cause of hyperthyroidism in the United States^[4]. It is an autoimmune disorder, which means your immune system mistakenly attacks your thyroid gland^[4]. In Graves’ disease, your body produces antibodies that stimulate all the cells in the thyroid gland to make too much thyroid hormone^[5]. This condition tends to happen more often in younger women and can run in families^[5].

Toxic multinodular goiter occurs when you have multiple lumps or growths of cells in your thyroid gland that produce excess thyroid hormone^[4]. Toxic adenoma (also called Plummer disease) happens when a single nodule or clump of cells in your thyroid becomes overactive and produces too much hormone^[4]. Thyroid nodules are more common in older adults and are rarely cancerous^[2].

Other less common causes of primary hyperthyroidism include thyroiditis (inflammation of the thyroid gland), consuming too much iodine through foods or medications, and certain drugs such as amiodarone^[2][4]. Very rarely, a tumor in the pituitary gland that releases excess TSH can cause hyperthyroidism^[2].

Symptoms

Hyperthyroidism speeds up your body’s metabolism, which can cause many different symptoms^[1]. You may experience some of these symptoms and not others, or many of them at the same time^[5]. Symptoms can start suddenly or develop slowly over time^[2].

Common symptoms of hyperthyroidism include^[1][2]:

• Losing weight without trying, even with a normal or increased appetite
• Fast or irregular heartbeat, sometimes with a pounding sensation (palpitations)
• Trembling, usually in your hands and fingers
• Nervousness, anxiety, and irritability
• Increased sweating and sensitivity to heat
• Tiredness and muscle weakness
• Difficulty sleeping
• More frequent bowel movements or diarrhea
• Changes in menstrual periods, often lighter or less frequent
• Thinning skin and brittle hair
• An enlarged thyroid gland, called a goiter, which may appear as a swelling at the base of your neck

People with Graves’ disease may also experience eye problems, including pain behind the eyes, swelling or bulging of the eyes, double vision, or increased sensitivity to light^[1][5].

Older adults, especially those over age 60, may have different symptoms than younger people^[6]. For example, they may lose their appetite or withdraw from other people. Sometimes these changes can be mistaken for depression or dementia^[6].

Who Is at Risk?

Primary hyperthyroidism is relatively rare, affecting approximately 1.3% of people in the United States^[2]. However, certain people have a higher risk of developing this condition.

You are at higher risk for hyperthyroidism if you^[6]:

• Are a woman—hyperthyroidism is about 10 times more common in women than men^[9]
• Are older than age 60
• Have been pregnant or had a baby within the past 6 months
• Have had thyroid surgery or a thyroid problem, such as a goiter
• Have a family history of thyroid disease
• Have another autoimmune condition, such as type 1 diabetes or primary adrenal insufficiency
• Have pernicious anemia, in which the body cannot make enough healthy red blood cells
• Consume too much iodine from foods, medications, or supplements

For Graves’ disease specifically, risk factors include female sex and a personal or family history of an autoimmune disorder^[4].

How Is It Diagnosed?

Doctors diagnose primary hyperthyroidism through a medical history, physical examination, and blood tests^[11]. During the physical exam, your healthcare provider may check for a slight tremor in your fingers and hands, overactive reflexes, rapid or irregular pulse, eye changes, and warm, moist skin^[11]. They will also examine your thyroid gland as you swallow to see if it’s larger than usual, bumpy, or tender^[11].

Blood tests measure the levels of thyroid hormones—T-4 (thyroxine) and T-3 (triiodothyronine)—and thyroid-stimulating hormone (TSH)^[11]. A high level of T-4 and a low level of TSH are common in people with hyperthyroidism^[11]. In primary hyperthyroidism, TSH levels are typically low (usually lower than 0.1 mU/L), while in secondary hyperthyroidism, TSH levels would be higher^[8].

If your blood tests show hyperthyroidism, your healthcare provider may suggest additional tests to find out why your thyroid is overactive^[11]. These may include:

• A radioiodine scan and uptake test, where you take a small dose of radioactive iodine to see how much collects in your thyroid gland and where it collects^[11]
• Testing for TSH-receptor antibodies (TRAb), which can confirm a diagnosis of Graves’ disease^[25]
• An ultrasound of your thyroid to check for nodules^[11]

Blood tests are particularly important for older adults because they may not have the classic symptoms of hyperthyroidism^[11].

Treatment Options

Primary hyperthyroidism is usually treatable^[9]. You will typically be referred to a specialist in hormonal conditions called an endocrinologist, who will plan your treatment^[12]. The choice of treatment depends on your age, symptoms, other health conditions, and personal preference^[4].

The three main treatments for primary hyperthyroidism are medicines, radioactive iodine treatment, and surgery^[12].

Medicines called antithyroid drugs are commonly used to treat an overactive thyroid^[12]. The main types are carbimazole and propylthiouracil. These medicines stop your thyroid from producing excess hormones^[12]. You’ll usually need to take the medicine for 12 to 18 months, and it may be a few months before you notice any benefit^[12]. Your doctor may also prescribe a beta blocker medicine to help relieve symptoms like rapid heartbeat while you wait for the antithyroid drugs to take effect^[21].

Radioactive iodine treatment is a type of therapy used to destroy the cells in the thyroid gland, reducing the amount of hormones it can produce^[12]. It is a highly effective treatment that can cure an overactive thyroid and is the most widely used treatment in the United States^[4]. You are given a drink or capsule that contains iodine and a low dose of radiation, which is absorbed by your thyroid^[12]. Most people only need a single treatment^[12]. After treatment, you’ll need to follow certain precautions, such as avoiding prolonged close contact with children and pregnant women for about 3 weeks^[12].

Surgery to remove all or part of your thyroid may be recommended in certain situations^[12]. This may be the best option if your thyroid gland is severely swollen, if you have severe eye problems caused by an overactive thyroid, if you cannot have other treatments, or if your symptoms return after trying other treatments^[12]. Removing all of the thyroid gland is usually recommended because it stops the symptoms from coming back^[12]. However, you will need to take medicine called levothyroxine for the rest of your life to replace the thyroid hormones your body can no longer produce^[12].

Potential Complications

If hyperthyroidism is not treated, it can cause serious health problems^[6]. These include:

• An irregular heartbeat that can lead to blood clots, stroke, heart failure, and other heart problems^[6]
• An eye disease called Graves’ ophthalmopathy, which can cause double vision, light sensitivity, and eye pain. In rare cases, it can lead to vision loss^[6]
• Thinning bones and osteoporosis^[6]
• Fertility problems in women^[6]
• Complications in pregnancy, such as premature birth, low birth weight, high blood pressure in pregnancy, and miscarriage^[6]
• A rare but life-threatening condition called thyroid storm, which is a sudden, severe flare-up of symptoms including very high fever, fast heartbeat, nausea, vomiting, diarrhea, extreme restlessness, and confusion^[21]

It is important to get medical treatment if you develop signs of hyperthyroidism so you can avoid these complications and get back to feeling like yourself^[2].