Principles of Treatment of Endocrine Disease in Animals
Endocrine diseases involving hyperactivity may be treated surgically (tumor removal), by radiotherapy (eg, 131I for feline hyperthyroidism), medically (eg, methimazole as an antithyroid drug; trilostane for hyperadrenocorticism), or by modifications in the diet (eg, iodine-deficient diet for feline hyperthyroidism). Syndromes of hormone deficiency are often successfully managed by simply replacing the missing hormone(s), such as insulin treatment in diabetes mellitus or thyroid hormone replacement therapy in hypothyroidism. Replacement therapy for deficiencies related to protein/polypeptide hormones can present a challenge. Often, the species-specific version of the hormone is not available, the drug may need to be injected several times per day, or the possibility of antibody formation and anaphylaxis must be considered. Steroid and thyroid hormones can usually be administered orally. Some protein/polypeptide hormones or analogues are effective when given by routes other than injection (eg, the antidiuretic hormone analogue desmopressin acetate is effective when administered by a variety of routes).
Hormonal replacement therapy should be monitored by assessment of clinical response and other suitable measures such as therapeutic blood monitoring (eg, post-pill measurement of T4 concentrations, measurement of sodium and potassium in serum in patients with primary hypoadrenocorticism). Replacement therapy is often required for a time after surgical removal of an endocrine tumor. However, remaining normal tissue that was atrophied as a consequence of the disease often recovers activity in a fairly short period of time, obviating need for lifelong replacement therapy. Animals show significant variation in drug bioavailability; thus, a proper dosing schedule should be tailored to each patient.
Glucocorticoids are commonly used therapeutic drugs, particularly because of their anti-inflammatory and anti-allergic activity. Proper use requires an understanding of their adverse effects, including the potential appearance of signs of hyperadrenocorticism resulting from longterm therapy or from use of potent derivatives. Such adverse effects can be minimized by use of orally administered glucocorticoids given on alternate days.
Once the diagnosis is established, most endocrine diseases can be treated successfully.
Multiple treatment options are available, even for a single disease (eg, feline hyperthyroidism can be treated in four ways; surgery, 131I, methimazole, or a diet deficient in iodine).
Monitoring of therapy usually involves a combination of clinical evaluation, hormone measurement, and biochemical monitoring.