To make the correct diagnosis if a hormonal disorder is suspected, the veterinary surgeon takes a blood sample to test for hormone levels.
Since the amount of the different hormones in the blood differs greatly both individually and in the course of a day or cycle, even in healthy creatures, a single measurement may not suffice. It is sometimes important to observe the course of the hormone level over a certain period, e.g., in the case of the sex hormones. Hormone tests are also used to analyse physiological processes in the body. Progesterone tests are an example. They are used in a bitch to establish the right time for mating.
One measurement, on the other hand, is often sufficient, e.g., when measuring thyroid overactivity in cats. To diagnose thyroid underactivity, which occurs mainly in dogs, other hormones are also measured at the initial stage. If disorders of cortisol metabolism are suspected, stimulation tests are performed. This means that a blood sample has to be taken before and a certain time after artificial (pharmacological) stimulation. An example of this is diagnosis of adrenocortical insufficiency (deficient production of adrenocortical hormone, Addison’s disease) or to determine the correct medication dosage to treat adrenocortical hormone over-production (Cushing’s syndrome).