To diagnose Cushing’s syndrome levels of free cortisol are checked in the urine. Levels of cortisol in the saliva and serum are checked at midnight to confirm the disease. Dexamethasone which is a synthetic glucocorticoid is administered which leads to decreased cortisol if the increased levels are due to a tumor in the anterior pituitary. Addisons disease is characterized by insufficiency of cortisol which is caused mostly due to production of antibodies against the adrenal gland within the body. This leads to decreased glucose metabolism in the body causing hypoglycemia and it can prove to be fatal in periods of stress and mild infections. Hyperpigmentation is also seen. Levels of free cortisol are checked in the urine and serum and saliva levels of cortisol are checked at midnight. Adrenocorticotropin hormone is then administered and levels of cortisol are measure. If they do not rise it indicates the insufficiency of the adrenal gland and rules out any problem with the anterior pituitary.
Radioimmunoassay is a technique in which a known quantity of labeled antibody and a labeled antigen is taken. This known complex is added to with unknown quantity of serum containing the antigens which needs to be measured. The unlabelled antigen displaces the labeled antigen and combines with the antibody. This unlabelled antigen and antibody is measured. Different quantities of serum are taken and added to the labeled complex and a graph is plotted and the values for the antigen in serum are measured. This method is extremely sensitive and specific because the antigen and antibody complexes formed are very specific for each other. It is also very sensitive because it can detect small amounts of antigen. The results obtained are accurate if many samples are taken. To improve accuracy it is important to purify the sample as well the reactants from foreign particles to prevent any false results. More samples