Two types of hypoadrenocorticism are recognized:
hypoadrenocorticism, which is thought to be related to a sudden reduction in stress which causes an exaggerated and rapid decrease in the production of endogenous adrenal hormones. The second type is hypoadrenocorticism, which can be thought The first type is of as adrenocorticoid hormone withdrawal. If the circulating levels of adrenocorticoid hormones are sustained through exogenous supplementation, the adrenal gland is not stimulated to produce hormones. This results in the of the adrenal gland. When the exogenous source of adrenocorticoid hormone is suddenly cut off the hypotrophic adrenal gland cannot produce sufficient amounts of corticoid hormone to sustain homeostasis. The medicinal use of is the most common source of exogenous adrenocorticoids. Horses who are put on stall or pasture rest due to injury sustained during prolonged and intense competition and those who are suddenly taken off of corticosteroid medications after prolonged use are predisposed to developing hypoadrenocorticism. The clinical presentation of hypoadrenocorticism includes weakness, lethargy, bradycardia, irregular heart rate, hypotension, dehydration, anorexia, diarrhea and renal failure. Ultrasound of the abdomen may reveal atrophy of the adrenal glands. Diagnosis can be made through case history, clinical signs and symptoms, serology revealing, hyperkalemia, hyponatremia, hypochloremia, hypoglycemia and normal levels of adrenocorticotropic hormone (ACTH) combined with depressed levels of circulating cortisol. If the circulating levels of ACTH are found to be low, an ACTH can be carried out where ACTH is administered and the adrenal gland’s ability to respond to stimulation by producing hormones is measured through serology. If the adrenal gland is unable to respond to exogenous ACTH the dysfunction must lie in the adrenal gland itself, not the pituitary which secretes ACTH. Treatment includes rest, decrease stress factors, IV fluids and administration of glucose. Corticosteriods should be administered and slowly wean the horse off to stimulate the adrenals to produce the hormones naturally.
Disorders of the Pituitary Gland
The pituitary gland has two lobes. The cranial lobe is called the , and is responsible for the secretion of growth hormone (GH)/somatotropin, prolactin, leutinizing hormone (LH), follicle stimulating hormone (FSH), thyroid stimulating hormone (TSH), adrenocorticotropic hormone (ACTH), and melanocyte stimulating hormone (MSH).
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