Persisting challenges in plasma endocrinology: reference values and endocrine tests.

The analysis of plasma hormone concentrations is of fundamental importance for the diagnosis and treatment of endocrine diseases. Although hormone analyses are performed in huge numbers in all hospitals on a daily basis, the interpretation of the resulting plasma hormone concentrations can be difficult. In addition to the effects of the underlying disease, biological and analytical issues affect hormone concentrations. Therefore, adequate reference values and strict standardisation of sampling and analytical procedures are very important for the final interpretation of the results of hormone analysis.