Hypothyroidism (underactive thyroid disease) is a condition that happens when your thyroid gland doesn’t make or release enough hormone into your bloodstream. As a result, your metabolism slows down. This can cause unintentional weight gain and make you feel exhausted all the time.

Types of hypothyroidism:

There are four main types of hypothyroidism:

• Primary hypothyroidism directly impacts your thyroid and causes it to make low levels of thyroid hormones. In turn, your pituitary gland makes more thyroid stimulating hormone (TSH). Autoimmune conditions like Hashimoto’s disease can cause it, or it can happen after thyroid gland surgery or radiation therapy. Primary hypothyroidism is the most common type.
• Secondary hypothyroidism occurs when you have an underactive pituitary gland (a pea-sized gland at the base of your brain). This rare type of hypothyroidism prevents your pituitary gland from sending TSH to your thyroid gland.
• Tertiary hypothyroidism happens when your hypothalamus (a structure in your brain that keeps your body in a stable state called homeostasis) doesn’t make enough thyrotropin-releasing hormone (TRH). As a result, your pituitary gland can’t make enough TSH.
• Subclinical hypothyroidism, also known as mild thyroid failure, happens when you have slightly elevated TSH levels, but all other thyroid hormone levels are within a typical range. Subclinical hypothyroidism usually goes away on its own in about three months.

What are the symptoms of hypothyroidism?

Brain fog (forgetfulness or difficulty concentrating). Depression and anxiety. Dry, coarse skin and hair. Elevated blood cholesterol levels. Feeling tired (fatigue). Frequent or heavy menstrual periods. Hoarseness. Inability to tolerate cold temperatures. Numbness or tingling in your hands. Physical changes in your face (drooping eyelids, puffiness around your eyes). Soreness or muscle weakness. Unexplained weight gain.

What causes hypothyroidism?

Certain medications, including lithium, thalidomide and amiodarone. Conditions present at birth, like being born with no thyroid gland or a thyroid gland that doesn’t work properly. Iodine deficiency (when you don’t have enough iodine in your body). Pituitary gland disorders, including noncancerous tumors. Thyroiditis (inflammation of the thyroid that can happen after a viral illness or pregnancy).

When should I see my healthcare provider? If you develop hypothyroidism symptoms like weight gain, dry skin or fatigue, let your healthcare provider know. They may want to run tests to rule out other conditions. If you already take medication for hypothyroidism, let your provider know if your symptoms come back or persist. They may need to adjust your dosage.