CHAPTER 34: ENDOCRINE DISEASE
Introduction The endocrine system is made up of a number of endocrine glands that synthesize, store and secrete directly into the bloodstream. The major function of the endocrine system is to control the function of target cell throughout the body, in this way controlling homeostasis, growth and physiological states such as reproductive maturity.
Dysfunction of the endocrine system is rare in horses, and is generally only seen in animals.
Most of the clinical signs and symptoms of endocrine dysfunction are generalized and do not give an indication of the specific type of pathology involved. Common signs of endocrine dysfunction include weight loss or gain, lethargy, alopecia, skin or hair abnormalities, changes in appetite, polydipsia, polyuria and behavioural changes. Diagnosis of endocrine pathologies is difficult due to generalized clinical presentation and the seeming dysfunction of multiple body systems simultaneously. Some techniques commonly used in the diagnosis of endocrine disease include case history, physical exam, haematology, serology including analysis of circulating hormone levels and specific tests to determine the function of particular glands. Disorders of the Adrenal Gland The adrenal glands are paired structures that are located bilaterally on the cranial aspect of the kidneys. The adrenal gland has two distinct regions, the outer cortex & the inner medulla. The adrenal cortex has three layers. The zona glomerulosa is the outermost layer that secretes hormones such as aldosterone. The zona fasiculata is the middle layer. It secretes glucocorticoid hormones like . The zona reticularis is the innermost layer that secretes hormones such as progesterone, estrogen, and androgens. The adrenal medulla plays a role in response to stress and hypoglycemia by secreting and norepinephrine. These hormones function to increase circulatory and respiratory function, decrease gastrointestinal activity and trigger the liberation of glucose stores.
Hypoadrenocorticism
Hypoadrenocorticism is also commonly called Addison’s syndrome, adrenal exhaustion or “let- down syndrome”. It is characterized by a in the amount of circulating hormones produced by the adrenal cortex.
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