Thyroid hormone is used to treat underactive thyroid (hypothyroidism). It is a natural product made from animal thyroid glands (usually a pig's). It replaces or provides more thyroid hormone, which is normally produced by the thyroid gland.
Foods high in potassium include bananas, spinach, carrots and oranges. Decreasing potassium intake can cause levels in the body to drop, but this is not a common reason for a decrease in potassium levels. Low potassium levels can occur when the body loses too much fluid due to illness. This fluid loss may occur because of excessive amounts of vomiting and diarrhea.
Some medications will decrease a potassium level. Taking prescription medications to rid the body of excess water, called diuretics, to help treat conditions such as kidney failure or high blood pressure can cause a drop in potassium, according to the Mayo Clinic. These medications force sodium and potassium to leave the body through urine.