Levothyroxine helps regulate your metabolism and energy, as it is a replacement for a hormone your thyroid normally produces that does this. Levothyroxine is used to treat low thyroid hormone levels in your body, called hypothyroidism.

A parasite is an organism that depends on a living host for its survival. Usually, the parasite derives all the benefit from the infection, to the detriment of the host. Parasitology is the study of this relationship between parasite and host.

Sudden anxiety can result from everyday situations or recurring problems. In severe cases it can lead to heart palpitations, shortness of breath, stomach aches, chest pain, nausea or dizziness. Fainting can also occur, due to increased blood pressure and blood flow.

Serotonin is a chemical produced by nerve cells in the brain. Low serotonin levels in the body are linked to instances of depression as well as insomnia.

If your doctor has prescribed Celexa (citalopram hydrobromide) for depression, you may wonder if the drug will affect your weight. Some antidepressant drugs can cause weight gain, a side effect that patients sometimes dislike so much that they stop taking their medication.

Adrenaline is one of the body's most important stress chemicals. It is secreted from the adrenal glands, which sit atop each kidney. Adrenaline also plays a key role as a neurotransmitter that facilitates communication between brain cells, or neurons, and other cells.

Depression affects more than 6 percent of the adult population in the United States. The National Alliance on Mental Illness warns that being single or widowed elevates the risk for this disorder.

If you have gluten intolerance, also known as celiac disease, you already know that you need to scrutinize labels of any products that might contain wheat, rye or barley. As little as one-eighth of a tsp. of the gluten protein found in these grains can set off a reaction.

Paranoia and depression do not commonly occur together, but when they do they can be signs of a serious underlying psychiatric condition.

Angina pectoris, or angina, is chest pain or discomfort that happens when a part of the heart does not get enough blood and oxygen. People who experience angina are at higher risk for a heart attack or cardiac arrest.

Depressant drugs are prescribed to relieve tension, anxiety and irritability. In addition, depressant drugs can treat insomnia. Orally taken, depressant drugs have a high potential for abuse, according to the U.S. Department of Health and Human Services.

The use of dietary supplements to treat various medical and mental health disorders is becoming more prevalent in recent years. In children with attention deficit hyperactivity disorder, or ADHD, the typical treatment is stimulant medication. However, some parents prefer to use natural treatments for their children.