Thursday, November 11, 2010

An Overview of Endocrine Disease in Dogs and Cats

Either “Too Much” or “Not Enough” of a Hormone

Endocrine diseases stem from imbalances in hormone levels. Hormone imbalances can affect your pet’s health in many ways.  Although some endocrine disorders are not life threatening, many are fatal if not diagnosed and treated.

Diseases can develop because an endocrine gland itself is faulty or because the control of that gland is faulty (i.e., a problem in the pituitary can harm the adrenal glands).  Endocrine diseases develop when the body produces too much hormone (hyper- diseases) or too little hormone (hypo- diseases).

A tumor or other abnormal tissue in an endocrine gland often causes it to produce too much hormone. Hormone excess disorders often begin with the prefix “hyper.” For example, in hyperthyroidism, the thyroid gland produces too much thyroid hormone.

Hormone excess (“Hyper”) disorders in dogs and cats
  • Pituitary tumors (most commonly, secrete too much growth hormone or ACTH)
  • Hyperthyroidism (secrete too much thyroid hormone)
  • Hypercalcemia (circulating calcium too high)
  • Hyperparathyroidism (secrete too much parathyroid hormone)
  • Pancreatic insulin-secreting tumor, usually called insulinoma (secrete too much insulin)
  • Hyperadrenocorticism, usually called Cushing’s syndrome (secrete too much cortisol)
  • Hyperaldosteronism, usually called Conn’s syndrome (secrete too much aldosterone)
  • Pheochromocytoma (secrete too much adrenaline)
  • Hypertension (blood pressure too high)
When an endocrine gland is destroyed, removed, or just stops working, not enough hormone is produced. Hormone deficiency disorders often begin with the prefix “hypo.” For example, in hypothyroidism, the thyroid gland does not produce enough thyroid hormone.

Hormone deficiency (“Hypo”) disorders in dogs and cats

  • Pituitary dwarfism (secrete too little growth hormone in young animals)
  • Diabetes insipidus (secrete too little antidiuretic hormone or vasspressin)
  • Hypothyroidism (secrete too little thyroid hormone)
  • Hypocalcemia (circulating calcium too low)
  • Hypoparathyroidism (secrete too little parathyroid hormone)
  • Diabetes mellitus (secrete too little insulin)
  • Hypoadrenocorticism, usually called Addison’s disease (too little cortisol and aldosterone secreted)
  • Hypotension (blood pressure too low)
Treating Endocrine Disease Again, Based on Either “Too Much” or “Not Enough” of a Hormone

Endocrine diseases caused by too much of a hormone can be treated surgically (tumor removal), with radiotherapy (such as the use of radioactive iodine to destroy an overactive thyroid gland), or with medications used to block the tumor from over-secreting the hormone.

One can normally treat hormone deficiency syndromes simply by supplementing the missing hormone.  For example, one can treat diabetes mellitus by giving insulin injections. Steroid and thyroid hormone replacements can usually be given orally.  Dogs and cats taking hormone replacement therapy must be monitored for side effects and periodically retested to make sure the drug dosage is correct. In some cases, such as after an endocrine tumor is surgically removed, the remaining gland will recover and hormone replacement will no longer be needed.
Unfortunately, most of these treatments are life-long.

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