Canine Endocrine Diseases

by Betty Lewis
    Cushing's disease and hypothyroidism are common endocrine disorders among older dogs.

    Cushing's disease and hypothyroidism are common endocrine disorders among older dogs.

    Ryan McVay/Photodisc/Getty Images

    The hormones in Pal's endocrine system are produced by the thyroid, parathyroid, pituitary and adrenal glands, and other organs, including his pancreas and testicles -- or ovaries if Pal's a female. Endocrine disease occurs when there are imbalances in the hormone levels. High hormone levels are "hyper" diseases; low hormone levels are "hypo."

    If Pal's thyroid gland isn't producing enough of the thyroid hormone, T4, he's hypothyroid. Typically, hypothyroidism is a result of damage to the thyroid gland, an immune related disease destroying the thyroid tissue or the gland's shrinkage. Fewer than 5 percent of hypothyroid dogs are secondary hypothyroidism, caused by a tumor on the gland. Symptoms of hypothyroidism include lethargy, weight gain and unwillingness to exercise. Hair loss, excessive shedding and skin dryness are common as well. The prognosis for detected hypothyroid is excellent, requiring synthetic hormone replacement for the dog's life. Hyperthyroidism is rare in dogs.

    If Pal's body isn't making or responding to insulin properly, he's at risk for diabetes mellitus. Insulin channels glucose from the bloodstream into the body's cells. If there's insufficient insulin, the glucose level remains high in the bloodstream, but the cells can't pick up the glucose, starving the cells. The symptoms of diabetes mellitus include increased urination and thirst. Untreated, diabetes can lead to cataracts, pancreatitis, weight loss and recurrent infections. Treatment involves a change in diet and daily insulin injections, resulting in a controllable condition requiring regular vet checks. Diabetes insipidus is caused by the pituitary gland anti-diuretic hormone ADH, which maintains the body's proper fluid level. If Pal has this form of diabetes, he'll urinate in large amounts and drink similar amounts of water. Lifelong medication is required.

    If Pal has a benign tumor in his pituitary gland increasing his cortisone level, he's prone to Cushing's disease, otherwise known as hyperadrenocorticism. Symptoms include increased hunger, thirst, urination and panting, obesity, lethargy, hair loss, muscle weakness, fat pads on the shoulders and neck, insomnia and blackheads on the skin. In many cases, treatment involves surgically removing the nonspreading tumor on his pituitary gland. Other treatment includes lifelong medication, requiring regular follow-up veterinary visits.

    Calcemia refers to the blood level in Pal's body. If he's hypercalcemic, his symptoms will depend on how much excess calcium he has. Common symptoms are increased thirst and urination, progressing to possible vomiting, constipation, decreased appetite, depression, weakness, seizures and muscle twitching. Since it's often caused by a different illness, such as tumors, kidney disease or Addison's disease, treatment varies. Hypocalcemia symptoms include muscle tremors, muscle contraction and convulsions. After determining what's causing the depleted calcium levels, calcium supplements and vitamin D usually are prescribed, along with treatment for the underlying cause.

    If Pal's adrenal gland isn't producing enough glucocorticoids and mineral corticoids, he's suffering from Addison's disease. His body doesn't adapt well to stress or maintain basic balance, resulting in symptoms such as vomiting, diarrhea, weakness and listlessness. This is a tough disease to diagnose, as the symptoms mimic a variety of other diseases. The dog with Addison's disease requires lifetime medication.

    When the pituitary gland isn't fully developed, a dog can be deficient in several hormones, resulting in pituitary dwarfism. Insulinoma is a tumor in a dog's pancreas secreting large volumes of insulin. Pheochromocytoma is an adrenal medulla tumor secreting adrenaline or noradrenaline. Hypogonadism affects a dog's sex glands, producing little or no sex hormones.

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    About the Author

    Betty Lewis is a writer and editor specializing in pet care, animals, careers and emergency management. She previously ran an animal shelter, where she also served as a kennel attendant and dog trainer. Lewis holds a bachelor's degree in journalism, an M.B.A. and a master's degree in professional studies.

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