Phenylketonuria (PKU) is a condition in which the body cannot break down one of the amino acids found in proteins. PKU is considered an amino acid condition because people with PKU cannot break down the amino acid called phenylalanine. If left untreated, PKU can cause brain damage or even death.our baby will need to be on a restricted diet to avoid phenylalanine, a building block of proteins that individuals with phenylketonuria (PKU) cannot break down. Phenylalanine is found in all foods that contain protein and also in artificial sweeteners.
In diagnosing hypothyroidism, your doctor will take into account both your symptoms and the results of a thyroid stimulating hormone (TSH) test. In essence, hypothyroidism is the result of diminished levels of thyroid hormonesâknown as T3 and T4.
Free thyroxine (free T4) tests are used to help evaluate thyroid function and diagnose thyroid diseases, including hyperthyroidism and hypothyroidism, usually after discovering that the thyroid stimulating hormone (TSH) level is abnormal. free T4 test may be used along with or following a TSH test and sometimes with a free T3 test to: 1  Help detect too much or too little thyroid hormone (hyperthyroidism and hypothyroidism) and diagnose the cause.