Hypothyroidism is when the thyroid gland does not produce enough thyroid hormones to meet the needs of the body. The thyroid is underactive.
The thyroid is a small, butterfly-shaped gland in the front of your neck. Thyroid hormones control the way the body uses energy, so they affect nearly every organ in your body, even the way your heart beats. Without enough thyroid hormones, many of your body’s functions slow down. Hormones are chemical messengers that relay information to the organs and tissues of the body, controlling processes such as metabolism, growth, and mood.
Causes of Hypothyroidism –
The most common cause of hypothyroidism is Hashimoto’s thyroiditis. “Thyroiditis” is an inflammation of the thyroid gland. Hashimoto’s thyroiditis is an autoimmune disorder. With Hashimoto’s, your body produces antibodies that attack and destroy the thyroid gland. Thyroiditis may also be caused by a viral infection.
Other causes of hypothyroidism include:
a) Radiation therapy to the neck area – Treating certain cancers, such as lymphoma, requires radiation to the neck. Radiation damages the cells in the thyroid. This makes it more difficult for the gland to produce hormone.
b) Radioactive iodine treatment – This treatment is commonly prescribed to people who have an overactive thyroid gland, a condition known as hyperthyroidism. However, radiation destroys the cells in the thyroid gland. This usually leads to hypothyroidism.
c) Use of certain medications- Certain medicines to treat heart problems, psychiatric conditions, and cancer can sometimes affect the production of thyroid hormone. These include amiodarone (Cordarone, Pacerone), interferon alpha, and interleukin-2.
d) Thyroid surgery – Surgery to remove the thyroid will lead to hypothyroidism. If only part of the thyroid is removed, the remaining gland may still be able to produce enough hormone for the body’s needs.
Too little iodine in the diet – The thyroid needs iodine to produce thyroid hormone. Your body doesn’t make iodine, so you need to get it through your diet. Iodized table salt is rich in iodine. Other food sources of iodine include shellfish, saltwater fish, eggs, dairy products, and seaweed. Iodine deficiency is rare in the U.S.
e) Pregnancy – The reason isn’t clear, but sometimes, inflammation of the thyroid occurs after pregnancy. This is called postpartum thyroiditis. Women with this condition usually have a severe increase in thyroid hormone levels followed by a sharp drop in thyroid hormone production. Most women with postpartum thyroiditis will regain their normal thyroid function.
f) Problems with the thyroid at birth – Some babies may be born with a thyroid gland that did not develop correctly or does not work properly. This type of hypothyroidism is called congenital hypothyroidism. Most hospitals in the U.S. screen babies at birth for this disease.
g) Pituitary gland damage or disorder – Rarely, a problem with the pituitary gland can interfere with the production of thyroid hormone. The pituitary gland makes a hormone, called thyroid-stimulating hormone (TSH), which tells your thyroid how much hormone it should make and release.
h) Disorder of the hypothalamus – An extremely rare form of hypothyroidism can occur if the hypothalamus in the brain does not produce enough of a hormone called TRH. TRH affects the release of TSH from the pituitary gland.
Primary hypothyroidism is caused by a problem with the thyroid gland itself.
Secondary hypothyroidism occurs when another problem interferes with the thyroid’s ability to produce hormones. For example, the pituitary gland or hypothalamus produce hormones that trigger the release of thyroid hormone. A problem with one of these glands can make your thyroid underactive.
Sometimes, an underactive thyroid that results from a problem with the hypothalamus is called tertiary hypothyroidism.
Symptoms of hypothyroidism –
1. Feeling Tired
One of the most common symptoms of hypothyroidism is feeling worn out. Thyroid hormone controls energy balance and can influence whether you feel ready to go or ready to nap.
Thyroid hormone receives signals from the brain and coordinates cells to change their functions, depending on what else is going on in your body.
Those with high levels of thyroid hormone feel nervous and jittery. In contrast, people with low thyroid feel exhausted and sluggish.
In one study, 138 adults with hypothyroidism experienced physical exhaustion and reduced activity. They also reported low motivation and feeling mentally tired.
Low-thyroid individuals feel unrested, even though they may be sleeping more.
In another study, 50% of people with hypothyroidism felt constantly tired, while 42% of people with low thyroid hormone said they slept more than they used to.
Feeling sleepier than usual without a good explanation could be a sign of hypothyroidism.
2. Gaining Weight
Unexpected weight gain is another common symptom of hypothyroidism.
Not only are low-thyroid individuals moving less — they’re also signaling their livers, muscles and fat tissue to hold on to calories.
When thyroid levels are low, metabolism switches modes. Instead of burning calories for growth and activity, the amount of energy you use at rest, or your basal metabolic rate, decreases. As a result, your body tends to store more calories from the diet as fat.
Because of this, low thyroid hormone levels can cause weight gain, even if the number of calories eaten remains constant.
In fact, in one study, people with newly diagnosed hypothyroidism gained an average of 15–30 pounds (7–14 kg) in the year since their diagnoses.
If you’ve been experiencing weight gain, first consider whether other changes in your lifestyle might explain it.
If you seem to be gaining weight in spite of a good diet and exercise plan, bring it up with your doctor. It might be a clue that something else is going on.
3. Weakness and Aches in Muscles and Joints
Low thyroid hormone flips the metabolic switch toward catabolism, which is when the body breaks down body tissues like muscle for energy.
During catabolism, muscle strength decreases, potentially leading to feelings of weakness. The process of breaking down muscle tissue can also lead to aching.
Everyone feels weak once in a while. However, people with hypothyroidism are twice as likely to feel more weak than usual, compared to healthy people.
4. Itchy and Dry Skin
Like hair follicles, skin cells are characterized by rapid turnover. Therefore, they are also sensitive to losing growth signals from the thyroid hormone.
When the normal cycle of skin renewal is broken, skin may take longer to regrow.
This means the outer layer of skin has been around longer, accumulating damage. It also means that dead skin may take longer to shed, leading to flaky, dry skin.
One study showed 74% of low-thyroid individuals reported dry skin. However, 50% of patients with normal thyroid levels also reported dry skin from other causes, making it hard to know if thyroid problems were the cause.
5. Feeling Down or Depressed
Hypothyroidism is linked to depression. The reasons for this are unclear, but it might be a mental symptom of an overall decrease in energy and health.
64% of women and 57% of men with hypothyroidism report feelings of depression. About the same percentage of men and women also experience anxiety.
In one study, thyroid hormone replacement improved depression in patients with mild hypothyroidism, compared to a placebo.
6. Trouble Concentrating or Remembering
Many patients with hypothyroidism complain of mental “fogginess” and trouble concentrating. The way this mental fogginess presents itself varies by person.
In one study, 22% of low-thyroid individuals described increased difficulty doing everyday math, 36% described thinking more slowly than usual and 39% reported having a poorer memory.
The causes for this are not yet fully understood, but difficulties in memory improve with treatment of low thyroid hormone.
Difficulties in memory or concentration can happen to everyone, but if they are sudden or severe, they could be a signal of hypothyroidism.
7. Constipation
Low thyroid levels put the brakes on your colon.
According to one study, constipation affects 17% of people with low thyroid hormone, compared to 10% of people with normal thyroid levels.
In this study, 20% of people with hypothyroidism said their constipation was getting worse, compared to only 6% of normal-thyroid individuals.
While constipation is a common complaint in patients with hypothyroidism, it’s uncommon for constipation to be the only or most severe symptom.
8. Heavy or Irregular Periods
Both irregular and heavy menstrual bleeding are linked to hypothyroidism.
One study showed that about 40% of women with low thyroid hormone experienced increasing menstrual irregularity or heavy bleeding in the last year, compared to 26% of women with normal thyroid levels.
Thyroid hormone interacts with other hormones that control the menstrual cycle, and abnormal levels of it can disrupt their signals. Also, thyroid hormone directly affects the ovaries and uterus.