Hypothyroidism, or underactive thyroid, happens when your thyroid gland doesn't make enough thyroid hormones to meet your body's needs.

Your thyroid is a small, butterfly-shaped gland in the front of your neck. It makes hormones that control the way the body uses energy. These hormones affect nearly every organ in your body and control many of your body's most important functions. For example, they affect your breathing, heart rate, weight, digestion, and moods. Without enough thyroid hormones, many of your body's functions slow down. But there are treatments that can help.

Hypothyroidism has several causes. They include:

• Hashimoto's disease, an autoimmune disorder where your immune system attacks your thyroid. This is the most common cause.
• Thyroiditis, inflammation of the thyroid
• Congenital hypothyroidism, hypothyroidism that is present at birth
• Surgical removal of part or all of the thyroid
• Radiation treatment of the thyroid
• Certain medicines
• In rare cases, a pituitary disease or too much or too little iodine in your diet

You are at higher risk for hypothyroidism if you:

• Are a woman
• Are older than age 60
• Have had a thyroid problem before, such as a goiter
• Have had surgery to correct a thyroid problem
• Have received radiation treatment to the thyroid, neck, or chest
• Have a family history of thyroid disease
• Were pregnant or had a baby in the past 6 months
• Have Turner syndrome, a genetic disorder that affects females
• Have pernicious anemia, in which the body cannot make enough healthy red blood cells because it does not have enough vitamin B12
• Have Sjogren's syndrome, a disease that causes dry eyes and mouth
• Have type 1 diabetes
• Have rheumatoid arthritis, an autoimmune disease that affects the joints
• Have lupus, a chronic autoimmune disease

The symptoms of hypothyroidism can vary from person to person and may include:

• Fatigue
• Weight gain
• A puffy face
• Trouble tolerating cold
• Joint and muscle pain
• Constipation
• Dry skin
• Dry, thinning hair
• Decreased sweating
• Heavy or irregular menstrual periods
• Fertility problems in women
• Depression
• Slowed heart rate
• Goiter, an enlarged thyroid that may cause your neck to look swollen. Sometimes it can cause trouble with breathing or swallowing.

Because hypothyroidism develops slowly, many people don't notice symptoms of the disease for months or even years.

Hypothyroidism can contribute to high cholesterol. In rare cases, untreated hypothyroidism can cause myxedema coma. This is a condition in which your body's functions slow down to the point that it becomes life-threatening.

During pregnancy, hypothyroidism can cause complications, such as premature birth, high blood pressure in pregnancy, and miscarriage. It can also slow the baby's growth and development.

Your health care provider may use many tools to make a diagnosis:

• A medical history, which includes asking about your symptoms
• A physical exam
• Thyroid tests, such as
  • TSH, T3, T4, and thyroid antibody blood tests
  • Imaging tests, such as a thyroid scan, ultrasound, or radioactive iodine uptake test. A radioactive iodine uptake test measures how much radioactive iodine your thyroid takes up from your blood after you swallow a small amount of it.

The treatment for hypothyroidism is medicine to replace the hormone that your own thyroid can no longer make. About 6 to 8 weeks after you start taking the medicine, you will get a blood test to check your thyroid hormone level. Your health care provider will adjust your dose if needed. Each time your dose is adjusted, you'll have another blood test. Once you find the right dose, you will probably get a blood test in 6 months. After that, you will need the test once a year.

If you take your medicine according to the instructions, you usually should be able to control the hypothyroidism. You should never stop taking your medicine without talking with your health care provider first.

If you have Hashimoto's disease or another type of autoimmune thyroid disorder, you may be sensitive to harmful side effects from iodine. Talk to your health care provider about which foods, supplements, and medicines you need to avoid.

Women need more iodine when they are pregnant because the baby gets iodine from the mother's diet. If you are pregnant, talk with your health care provider about how much iodine you need.

NIH: National Institute of Diabetes and Digestive and Kidney Diseases

Healthy kidneys clean your blood by removing excess fluid, minerals, and wastes. They also make hormones that keep your bones strong and your blood healthy. But if the kidneys are damaged, they don't work properly. Harmful wastes can build up in your body. Your blood pressure may rise. Your body may retain excess fluid and not make enough red blood cells. This is called kidney failure.

If your kidneys fail, you need treatment to replace the work they normally do. The treatment options are dialysis or a kidney transplant. Each treatment has benefits and drawbacks. No matter which treatment you choose, you'll need to make some changes in your life, including how you eat and plan your activities. But with the help of health care providers, family, and friends, most people with kidney failure can lead full and active lives.

NIH: National Institute of Diabetes and Digestive and Kidney Diseases

You have two kidneys. They are fist-sized organs on either side of your backbone above your waist. Your kidneys filter and clean your blood, taking out waste products and making urine. Kidney tests check to see how well your kidneys are working. They include blood, urine, and imaging tests.

Early kidney disease usually does not have signs or symptoms. Testing is the only way to know how your kidneys are doing. It is important for you to get checked for kidney disease if you have the key risk factors - diabetes, high blood pressure, heart disease, or a family history of kidney failure.

Specific kidney tests include:

• Glomerular filtration rate (GFR) - one of the most common blood tests to check for chronic kidney disease. It tells how well your kidneys are filtering.
• Creatinine blood and urine tests - check the levels of creatinine, a waste product that your kidneys remove from your blood
• Albumin urine test - checks for albumin, a protein that can pass into the urine if the kidneys are damaged
• Imaging tests, such as an ultrasound - provide pictures of the kidneys. The pictures help the health care provider see the size and shape of the kidneys, and check for anything unusual.
• Kidney biopsy - a procedure that involves taking a small piece of kidney tissue for examination with a microscope. It checks for the cause of kidney disease and how damaged your kidneys are.

NIH: National Institute of Diabetes and Digestive and Kidney Diseases

Medicines can treat diseases and improve your health. If you are like most people, you need to take medicine at some point in your life. You may need to take medicine every day, or you may only need to take medicine once in a while. Either way, you want to make sure that your medicines are safe, and that they will help you get better. In the United States, the Food and Drug Administration is in charge of ensuring that your prescription and over-the-counter medicines are safe and effective.

There are always risks to taking medicines. It is important to think about these risks before you take a medicine. Even safe medicines can cause unwanted side effects or interactions with food, alcohol, or other medicines you may be taking. Some medicines may not be safe during pregnancy. To reduce the risk of reactions and make sure that you get better, it is important for you to take your medicines correctly. You should also be careful when giving medicines to children, since they can be more vulnerable to the effects of medicines.

Muscle cramps are sudden, involuntary contractions or spasms in one or more of your muscles. They are very common and often occur after exercise. Some people get muscle cramps, especially leg cramps, at night. They can be painful, and they may last a few seconds to several minutes.

You can have a cramp in any muscle, but they happen most often in the:

• Thighs
• Feet
• Hands
• Arms
• Abdomen
• Area along your ribcage

Causes of muscle cramps include:

• Straining or overusing a muscle. This is the most common cause.
• Compression of your nerves, from problems such as a spinal cord injury or a pinched nerve in the neck or back
• Dehydration
• Low levels of electrolytes such as magnesium, potassium, or calcium
• Not enough blood getting to your muscles
• Pregnancy
• Certain medicines
• Getting dialysis

Sometimes the cause of muscle cramps is unknown.

Anyone can get muscle cramps, but they are more common in some people:

• Older adults
• People who are overweight
• Athletes
• Pregnant women
• People with certain medical conditions, such as thyroid and nerve disorders

Muscle cramps are usually harmless, and they go away after a few minutes. But you should contact your health care provider if the cramps:

• Are severe
• Happen frequently
• Don't get better with stretching and drinking enough fluids
• Last a long time
• Are accompanied by swelling, redness, or a feeling of warmth
• Are accompanied by muscle weakness

You usually don't need treatment for muscle cramps. You may be able to find some relief from cramps by:

• Stretching or gently massaging the muscle
• Applying heat when the muscle is tight and ice when the muscle is sore
• Getting more fluids if you are dehydrated

If another medical problem is causing the cramps, treating that problem will likely help. There are medicines that providers sometimes prescribe to prevent cramps, but they are not always effective and may cause side effects. Talk to your provider about the risks and benefits of medicines.

To prevent muscle cramps, you can:

• Stretch your muscles, especially before exercising. If you often get leg cramps at night, stretch your leg muscles before bed.
• Drink plenty of liquids. If you do intense exercise or exercise in the heat, sports drinks can help you replace electrolytes.