There are number of possible causes for both.

CPK
CPK stands for creatine phosphokinase. It is an enzyme found in muscle. A high CPK raises the possibility of a muscle disease. Testing is not routine. It is generally used when there is a concern about muscle injury or disease.

Because elevated CPKs come up so often I created a pneumonic ("I'M TIRED") to help me remember some of the most common causes:

• Idiopathic -- This means no cause can be found. Some people have a higher than average level even though they are healthy and have no muscle disease.
• Myocardial (heart) or metabolic muscle disease -- Examples include a heart attack or one of the muscular dystrophies.
• Trauma -- A major injury can damage muscle enough to cause an elevated level in the blood.
• Infection -- A number of viruses, bacteria and other organisms can infect muscle and cause an elevated CPK.
• Rheumatic disease -- Examples include dermatomyositis or polymyositis. These are conditions in which the immune system attacks the muscle and causes inflammation and damage in muscle tissue.
• Endocrine (hormonal) disease -- The most common one causing high CPK is an underactive thyroid (hypothyroidism).
• Drug -- Cholesterol-lowering statins are the most common culprits, but many drugs can cause a high CPK.

Phosphorus
An elevated phosphate level (called hyperphosphatemia) is usually related to impaired kidney function. Normally, the kidneys get rid of excess phosphate. Blood levels of phosphate begin to rise as kidney function falls.

Rarer causes include:

• Hypoparathyroidism (a deficiency in the parathyroid hormone) and pseudohypoparathyroidism (when the kidneys lose their ability to respond to parathyroid hormone). This hormone is made by the parathyroid glands in the neck. It helps regulate calcium and phosphate in the body. A deficiency or poor function tells the kidneys to excrete less phosphate so blood levels rise.
• Use of certain medications, including laxatives or enemas that contain phosphate
• Low blood calcium -- Because blood levels of calcium and phosphate tend to change in opposite directions (one goes up when the other goes down), an abnormally low blood calcium, as may be seen in vitamin D deficiency or kidney disease, often leads to higher blood phosphate levels.
• Muscle injury or tumor cell breakdown (which can follow chemotherapy) may release phosphate into the bloodstream.

If you have a high CPK and phosphate, talk to your doctor about the possible causes and appropriate treatment. It may turn out to be nothing important. Mild elevations may be found in healthy people, but many of these conditions are important to identify and treat.