Inherited endocrine disorders

Mellitus

roblib — Wed, 31 Mar 2010 18:17:48 +0000

What is ... ?:

Diabetes mellitus is a disruption of the body's ability to use carbohydrates/sugars. Normally, certain cells in the pancreas produce the hormone insulin which regulates the uptake of sugars into cells throughout the body. In some forms of diabetes mellitus, the cells are dysfunctional and do not produce insulin, while in other forms insulin is produced but body tissues do not respond appropriately.

Genetics is only one of many factors that may be involved. In some dogs there seems to be a genetic predisposition to to the destruction by the immune system of the insulin-producing cells. In other dogs, less severe genetic-based changes in the cells may make the dog more susceptible to the development of diabetes mellitus - in association with another illness or obesity or exposure to certain drugs.

How is ... inherited?:

In keeshonds, diabetes mellitus is inherited as an autosomal recessive trait. The mode of inheritance has not been determined in other breeds.

What breeds are affected by ... ?:

West Highland white terrier

What does ... mean to your dog & you?:

In dogs with the most severe form of inherited diabetes mellitus, signs are usually apparent by 6 months of age. Pups drink and eat more than normal, and yet grow very slowly. They urinate frequently, and their stools are soft.

In other dogs, diabetes mellitus does not develop until middle age. The signs of uncomplicated diabetes are typical - increased eating, drinking, and urination, with weight loss - all of which are a result of increased levels of glucose in the blood and urine. Over the long term, this can lead to the development of cataracts, increased susceptibiIity to bacterial infections (especially of the urinary tract), liver disease, and pancreatitis. Eventually, untreated diabetic dogs will develop ketoacidosis, a very serious condition. Signs of ketoacidosis include depression, weakness, vomiting, and irregular breathing patterns.

How is ... diagnosed?:

The diagnosis is made based on the typical clinical signs - increased eating, drinking, and urination, with weight loss - together with persistently elevated levels of glucose in both the blood and the urine. Ketones may also be present in the urine. Your veterinarian will do a complete laboratory work-up, to see if there is any other condition that may be causing or contributing to, or occurring as a result of, the diabetes mellitus. S/he may start your dog on insulin treatment before receiving all the laboratory results.

How is ... treated?:

In the diabetic dog without any other illness, the goals of therapy are to achieve near-normal blood glucose levels and minimize the daily variation in those levels. This is important to prevent the complications that develop over time in poorly controlled diabetic patients. Treatment includes insulin administration, diet, and exercise, all of which your veterinarian will discuss with you.
Emergency treatment for dogs with ketoacidois includes intravenous fluids and fast-acting insulin. Once the animal is stable, a regular regime of longer-acting insulin, diet, and exercise can be established.

For the veterinarian:

LABORATORY FINDINGS: fasting hyperglycemia with glucosuria; if the dog has ketoacidosis may see metabolic acidosis, hyponatremia, hyperkalemia, and hypochloremia.

Breeding advice:

In keeshonds, both parents of affected dogs should be considered carriers and should not be used for further breeding. In other breeds, where less is known about the inheritance of this condition, affected dogs should not be bred, and parents and siblings should be considered potential carriers.

FOR MORE INFORMATION ABOUT THIS DISORDER, PLEASE SEE YOUR VETERINARIAN.

Resources:

Nelson, R.W. 1995. Diabetes Mellitus. In S.J. Ettinger and E.C. Feldman (eds.). Textbook of Veterinary Internal Medicine, p. 1510-1537. W.B. Saunders Co., Toronto.

Growth hormone-responsive dermatosis; adrenal sex hormone responsive dermatosis

roblib — Wed, 31 Mar 2010 18:21:19 +0000

What is ... ?:

With this condition there are skin changes due to a lack of growth hormone (somatotropin). This hormone is secreted by the pituitary gland and is necessary for hair growth and the maintenance of normal elasticity of the skin. Affected dogs have varying degrees of hair loss and darkening of the skin, but are otherwise healthy.

Adrenal sex-hormone dermatosis is a clinically similar syndrome that appears to be due to abnormal sex hormone production by the adrenal glands, causing secondary changes in growth hormone levels.

How is ... inherited?:

A mode of inheritance has not been established; however the disorder is mostly seen in the breeds listed below.

What breeds are affected by ... ?:

What does ... mean to your dog & you?:

This condition is more common in male dogs between 1 and 5 years of age, with hair loss usually starting at puberty. Adrenal sex-hormone dermatosis is seen in males and females, either neutered or intact.

Hair loss (called alopecia) is symmetrical over the trunk of the dog and the skin is markedly darker in color due to increased pigmentation. Without treatment, hairlessness and hyperpigmentation will eventually spread over your dog's body except for head and feet. The condition does not affect the health of your dog, only his/her appearance.

How is ... diagnosed?:

There are several possible hormonal causes of hair loss in dogs. Your veterinarian will do tests to determine the cause in your pet.

How is ... treated?:

As mentioned, this condition does not affect the health of your dog, only his/her appearance. It can be treated with growth hormone (GH), but this is expensive and can be difficult to obtain. Treated dogs must be monitored for the development of diabetes mellitus which is a potential side effect of GH therapy. Castration may resolve the condition in male dogs.

Similarly, neutering of affected male or female dogs may help to treat adrenal sex-hormone imbalance. If ineffective, there are medical treatments that may be beneficial (opDDD or mitotane, and ketoconazole).

For the veterinarian:

Other endocrinologic causes of alopecia (hypothyroidism, hyperadrenocorticism) should be ruled out. Assessment of growth hormone or serum insulin-like growth factor (IGF) in response to a growth hormone stimulant such as xylazine or medetomidine is available in some laboratories [check with your diagnostic laboratory].

In adrenal sex-hormone dermatosis, elevations in sex hormone levels are seen post- ACTH stimulation.
Histopathologic changes are non-specific - normal to decreased skin thickness with atrophy of follicles, with or without a loss of elastin fibers.

Breeding advice:

Although little is known about the inheritance of this disorder, it is prudent to avoid breeding affected animals or their close relatives.

FOR MORE INFORMATION ABOUT THIS DISORDER, PLEASE SEE YOUR VETERINARIAN.

Resources:

Schmeitzel, L., Lothrop, C.D., Rosencrantz, . 1995. Congenital adrenal hyperplasia-like syndrome. In J.D. Bonaguara and R.W. Kirk (eds.) Kirk's Current Veterinary Therapy XII Small Animal Practice. p. 600-604. W.B. Saunders Co., Toronto.

Hyperadrenocorticism (Cushing's syndrome)

roblib — Wed, 31 Mar 2010 18:46:24 +0000

What is ... ?:

Hyperadrenocorticism, also known as Cushing's syndrome, is a common endocrine disorder in dogs. The clinical signs are caused by an excess of cortisol (the body's form of cortisone). This occurs because of increased secretion of cortisol by the adrenal glands in response to an abnormality in the pituitary gland in the brain, or because of a tumour in the adrenal glands themselves. Cushing's syndrome is more common in certain breeds, usually in dogs that are 6 years of age or older.

Hyperadrenocorticism may also occur in any dog that is being treated with excessive amounts of glucocorticoids. Glucocorticoid medication, often called steroids, is an important part of therapy in many different conditions in dogs.

How is ... inherited?:

unknown

What breeds are affected by ... ?:

What does ... mean to your dog & you?:

Cortisol affects many body functions including the metabolism of protein, carbohydrate and fat, the immune response, and the inflammatory response. Because of this, there are a wide variety of signs which may be associated with this disorder. Hyperadrenocorticism is insidious in onset and progresses slowly.

Usually the first signs are a gradual increase in appetite, drinking and urination. These changes may be overlooked until other abnormalities are noticed such as symmetrical hair loss over the trunk of the body, thinning skin, muscle wasting, a pendulous abdomen, panting, and an inflammatory skin condition called calcinosis cutis. Poor wound healing and an increased susceptibility to skin infections are also common.

How is ... diagnosed?:

Diagnosis is based on typical clinical signs as described above, laboratory abnormalities, and adrenal function tests which will help your veterinarian to determine if the disease is caused by abnormal pituitary stimulation of the adrenal glands, or by an adrenal tumour.

How is ... treated?:

If an adrenal tumour can be identified, it may be possible to remove it surgically, depending on the location and size of the tumour and whether it is benign or malignant.

For hyperadrenocorticism due to pituitary disease, or for inoperable adrenocortical tumours, medical treatment is used. There are several effective drugs available to decrease the production of cortisol by destroying part of the adrenal gland or by blocking synthesis. Your veterinarian will tell you what to expect with the use of these drugs and will monitor your dog's response to treatment carefully. Improvement in some clinical signs (more normal appetite and water intake) occurs quickly; reversal of skin and hair coat changes often takes 3 to 6 months; clinical pathological changes (elevations in liver enzymes for example) may take even longer to resolve.

For the veterinarian:

CLINICAL PATHOLOGY: There are a wide variety of abnormalities seen that are consistent with hyperadrenocorticism. Concurrent medical problems, secondary to Cushing's disease, may also be identified.
ULTRASONOGRAPHY: A skilled radiologist can usually visualize the adrenal glands to evaluate the size and shape, and, if an adrenal mass is seen, can screen for hepatic or other organ metastasis
DISCRIMINATION TESTS: ACTH stimulation test, low-dose dexamethasone test, high-dose dexamethasone suppression test - these tests can be used to discriminate between pituitary dependent and adrenocortical tumour hyperadrenocorticism [see reference below for detailed discussion]

Breeding advice:

Since little is known about the inheritance of this condition, the best advice for prevention is to select breeding dogs from families with no history of the disorder.

FOR MORE INFORMATION ABOUT THIS DISORDER, PLEASE SEE YOUR VETERINARIAN.

Resources:

Feldman, E.C. 1995. Hyperadrenocorticism. In S.J. Ettinger and E.C. Feldman (eds.) Textbook of Veterinary Internal Medicine p. 1538-1578. W.B. Saunders Co., Toronto.

Hypoadrenocorticism (Addison's disease)

roblib — Wed, 31 Mar 2010 18:52:58 +0000

What is ... ?:

Hypoadrenocorticism (Addison's disease) is a rare but serious disorder of the endocrine system caused by the gradual destruction of the cortex of the adrenal gland, most commonly by the body's immune system . (Cancer, hemorrhage, or certain drugs can also cause adrenocortical destruction.) The result is a decrease in production of glucocorticoids and mineralocorticoids - adrenal hormones that are necessary for a wide range of body functions. Deficient production of these hormones produces a diverse array of clinical signs, many of them vague.

The condition is more common in young female dogs and in the breeds listed below.

How is ... inherited?:

unknown.

What breeds are affected by ... ?:

What does ... mean to your dog & you?:

Mineralocorticoids and glucocorticoids normally produced by the adrenal gland are instrumental in regulating many body functions. A deficiency of these hormones therefore causes a variety of clinical signs. The most common problems noticed by owners include depression, weakness, loss of appetite, shaking or shivering, vomiting, diarrhea, and increased thirst and urination. Your dog may experience any or all of these and with varying degrees of severity.

When these vague signs go unnoticed or undiagnosed, dogs with hypoadrenocorticism may become seriously ill very quickly, developing acute adrenocortical insufficiency (Addisonian crisis). This is a life-threatening medical emergency requiring immediate treatment to correct the dehydration and electrolyte imbalances present.

How is ... diagnosed?:

Because of the variety of clinical signs, hypoadrenocorticism is often difficult to diagnose. Commonly dogs with this condition will have a history of vague illnesses associated with periods of stress, that responded to non-specific treatment and supportive care such as cage rest, or giving intravenous fluids to treat dehydration.

Ultimately diagnosis is made based on the combination of clinical signs, suggestive results of routine blood tests, and the results of a specific test for this disorder.

How is ... treated?:

Dogs with hypoadrenocorticism are treated with lifelong mineralocorticoid supplements, often with glucocorticoids as well. Your veterinarian will measure your dog's electrolyte levels regularly until the appropriate dose is found, and then sporadically after that. Hypoadrenocorticism can usually be well-controlled in this way although you should be alert to signs of relapse or illness in your dog, particularly during periods of stress (such as surgery or trauma).

Dogs in collapse with acute adrenocortical insufficiency must be treated immediately with intravenous glucocorticoids and large volumes of intravenous fluids to correct dehydration and electrolyte imbalances. Your veterinarian may start giving your dog oral mineralocorticoids at this time, or wait until your dog is stable.
For the veterinarian: Most electrolyte imbalances are corrected by rapid fluid and glucocorticoid administration. Severe metabolic acidosis, hypoglycemia and hyperkalemia causing cardiac conduction abnormalities may require additional therapy, and should be treated as necessary if not responding.

For the veterinarian:

CLINICAL PATHOLOGY: typically see hyponatremia, hyperkalemia, and hypochloremia. Dogs often have a normochromic, normocytic, nonregenerative anemia (possibly masked by dehydration), and prerenal azotemia. Dogs in hypoadrenal crisis typically have a Na/K ratio of less than 20, and often show hypercalcemia and mild to moderate acidosis.

Diagnosis is by measurement of cortisol pre- and post-ACTH (ACTH stimulation test).
ELECTROCARDIOGRAM: Changes typically reported with hyperkalemia (eg. small or absent P waves) correlate poorly with serum potassium levels in dogs with hypoadrenocorticism.

Breeding advice:

Although little is known about the inheritance of this disorder, it is prudent to avoid breeding affected animals or their close relatives.

FOR MORE INFORMATION ABOUT THIS DISORDER, PLEASE SEE YOUR VETERINARIAN.

Resources:

Kintzer, PP and Peterson, ME. 1995. Hypoadrenocorticism in dogs. In JD Bonagura and R Kirk (eds) Kirk's Current Veterinary Therapy XII Small Animal Practice. p 425-429. WB Saunders Co. , Toronto.

Hypothyroidism

roblib — Thu, 01 Apr 2010 17:12:48 +0000

What is ... ?:

The clinical signs of hypothyroidism are caused by a decrease in normal thyroid hormone activity. The disorder may be acquired (a progressive deficiency of thyroid hormone) or congenital (meaning the animal is born with the disorder). The acquired form is the most common disorder of the endocrine system in dogs. It occurs as a result of gradual atrophy of the thyroid gland or of gradual infiltration and replacement of the thyroid gland with lymphocytes due to an autoimmune process (lymphocytic thyroiditis).

Acquired hypothyroidism is generally seen in middle-aged (4 to 10 years) mid - to large breed dogs. Congenital hypothyroidism is very rare.

How is ... inherited?:

unknown

What does ... mean to your dog & you?:

The changes due to gradually decreasing levels of circulating thyroid hormone are slow and insidious. Early signs (which are usually not recognized as being related to hypothyroidism) include lower energy levels and increased susceptibility to infections. As the disease progresses, you will likely notice changes in your dog's hair coat - symmetrical hair loss with or without darkening of the skin, and dry or greasy hair. Other signs of hypothyroidism include a slow heart rate, lethargy, mental dullness, intolerance to cold, infertility in males and females, constipation, and weight gain. Less commonly, a dog with hypothyroidism may experience heart disease, a bleeding disorder, profound muscular weakness associated with abnormalities in the muscles or nerves, or another endocrine disorder such as diabetes mellitus.

Congenital hypothyroidism
Thyroid hormones are essential for normal growth and maturation of the nervous and skeletal systems. Puppies with congenital hypothyroidism will have stunted growth as well as many other abnormalities. Severely affected puppies most likely die before weaning.

How is ... diagnosed?:

Because there is such a broad range of possible clinical signs, hypothyroidism can be quite difficult to diagnose. Blood tests may show certain suggestive (but non-specific) abnormalities. If your veterinarian suspects this condition, s/he will perform laboratory tests to assess thyroid function.

How is ... treated?:

The standard treatment is levo-thyroxine given once a day. This must be continued for life. Within a week of starting treatment, your dog's attitude and activity levels should improve. It can take up to 6 weeks before there is noticeable improvement in the skin and haircoat, but eventually all abnormalities should completely resolve.

Dogs on thyroid replacement can live a normal life. Your veterinarian will monitor thyroid hormone levels periodically and adjust the dose if required. Certain other illnesses may also necessitate dosage adjustment.
Congenital hypothyroidism is treated the same way. Clinical signs are usually completely reversed with subsequent normal physical and mental growth and development, as long as the condition is recognized and treatment started very early (3 to 4 months of age).

For the veterinarian:

CLINICAL PATHOLOGY: Suggestive findings include hypercholesteremia, mild nonregenerative anemia, elevated serum creatine kinase (CK), and hypoglycemia
CONFIRMATION: Measurement of free T4 (FT4) and canine thyroid-stimulating hormone (cTSH) are the tests of choice to diagnose hypothyroidism, and to differentiate the primary from the secondary form. [Secondary hypothyroidism is much less common.] Some laboratories can also test for thyroid autoantibody levels (TgAA) which is helpful in the early diagnosis of autoimmune thyroiditis. This may provide useful information for breeders. [See reference 2 for a good discussion of tests.]
RADIOGRAPHS: In congenital hypothyroidism, there are typical radiographic changes including epiphyseal closure, shortened vertebral bodies, kyphosis, and arthritis. Epiphyseal dysgenesis (ragged epiphyses with a few foci of calcification) is pathognomonic for congenital hypothyroidism.

Breeding advice:

Although inheritance of this disorder has not been determined, it is advisable not to breed affected dogs. The OFA (Orthopedic Foundation for Animals) maintains a thyroid registry based on assessment of FT4, cTSH, and TgAA, which is useful for breeders attempting to choose dogs free of hypothyroidism for a breeding programme.

FOR MORE INFORMATION ABOUT THIS DISORDER, PLEASE SEE YOUR VETERINARIAN.

Resources:

Chastain, C.B., Panciera, D.L. 1995. Hypothyroid diseases. In S.J. Ettinger and E.C. Feldman (eds.) Textbook of veterinary Internal medicine. p. 1487-1501. W.B. Saunders Co., Toronto.

Peterson ME, Melian C, Nichols R. Measurement of serum total thyroxine, triodothyronine, free thyroxine, and thyrotropin concentrations for diagnosis of hypothyroidism in dogs. JAVMA 1997; 211(11):1396-1402. This reference clearly explains the different tests available, and the significance and interpretation of the results.

Orthopedic Foundation for Animals: www.offa.org

Juvenile hyperparathyroidism

roblib — Thu, 01 Apr 2010 17:18:32 +0000

What is ... ?:

This condition is one of abnormally increased activity of the parathyroid glands, which are important in the regulation of calcium and phosphorus in the body. The excess of parathyroid hormone causes problems in the bones and kidneys.

How is ... inherited?:

The condition is believed to be inherited as an autosomal recessive trait.

What does ... mean to your dog & you?:

Affected dogs will have stunted growth, increased urination and drinking, and muscle weakness.

How is ... diagnosed?:

Your veterinarian will do laboratory blood tests to determine the cause of your dog's stunted growth, usually the most obvious sign of this disorder.

How is ... treated?:

There are 4 parathyroid glands, 2 associated with each thyroid gland in the neck region. One to 3 of these can be removed surgically to correct the hyperparathyroidism but leave enough parathyroid tissue to carry out normal functions.

For the veterinarian:

CLINICAL PATHOLOGY: hypophosphatemia with increased fractional clearance of phosphorus, elevated plasma PTH, hypercalcemia. R/O hyper- or hypovitaminosis D, bone neoplasia, and osteomyelitis.

RADIOGRAPHS may show decreased bone density.

Breeding advice:

Parents of affected dogs should not be bred as they are carriers of the disorder. There is a 50 per cent chance that siblings are carriers as well.

FOR MORE INFORMATION ABOUT THIS DISORDER, PLEASE SEE YOUR VETERINARIAN.

Resources:

Greco, D.S. 1995. Pediatric Endocrinology. In J.D. Bonaguara and R.W. Kirk (eds.) Kirk's Current Veterinary Therapy XII Small Animal Practice. p 346-351. W.B. Saunders Co., Toronto.

Pituitary dwarfism

roblib — Tue, 13 Apr 2010 17:18:05 +0000

What is ... ?:

This rare disorder is a result of reduced function of the pituitary gland, which is located at the base of the brain. This small gland secretes hormones necessary for normal growth and development. Signs are apparent at a young age and are associated with slowed development and growth.

How is ... inherited?:

In German shepherds and Carnelian bear dogs the disorder is inherited as a simple autosomal recessive trait. The mode of inheritance has not been demonstrated for other affected breeds.

What breeds are affected by ... ?:

What does ... mean to your dog & you?:

Breeders or owners will usually notice abnormalities by 2 or 3 months of age. The signs caused by a deficiency of pituitary growth hormone (somatotropin) include slow growth rate, retained puppy coat and eventual hairlessness, darkening of the skin, delayed eruption of permanent teeth, suppressed immune responses, and an altered mental state. These pups are proportionate dwarves - that is, they are of small stature but normal proportions - and they often have a shrill bark.

Other hormones produced by the pituitary gland are also decreased and this causes abnormalities in thyroid, adrenal, and gonadal function.
Most dogs affected with this condition will have shortened lifespans.

How is ... diagnosed?:

The diagnosis is usually made based on the history and characteristic clinical signs in a young dog. Your veterinarian will want to rule out other possible causes of delayed growth.

How is ... treated?:

Dogs are treated with replacement growth hormone (GH), which is expensive and difficult to obtain. Treated dogs must be monitored for the development of diabetes mellitus which is a potential side effect of GH therapy. Secondary hypothyroidism and hypoadrenocorticism can also be treated if indicated.

For the veterinarian:

CLINICAL PATHOLOGY: may see a mild normochromic, normocytic anemia, hypoglycemia (secondary to ACTH deficiency), and hypophosphatemia (secondary to GH deficiency); often routine clinicopathologic tests show no significant abnormalities
GROWTH HORMONE CONCENTRATIONS: Growth hormone assays or serum insulin-like growth factor (IGF) assays may be available in some laboratories [check with your diagnostic laboratory].

Breeding advice:

This condition is generally apparent before dogs are sold. Breeders should avoid breeding parents of affected dogs.

FOR MORE INFORMATION ABOUT THIS DISORDER, PLEASE SEE YOUR VETERINARIAN.

Resources:

Nichols, R., Thompson, L. 1995. Pituitary-hypothalmic disease. In S.J. Ettinger and E.C. Feldman (eds.) Textbook of Veterinary Internal Medicine. p. 1422-1436. W.B. Saunders Co., Toronto.

Diabetes mellitus

roblib — Thu, 13 May 2010 18:00:13 +0000

What is ... ?:

How is ... inherited?:

In keeshonds, diabetes mellitus is inherited as an autosomal recessive trait. The mode of inheritance has not been determined in other breeds.

What breeds are affected by ... ?:

What does ... mean to your dog & you?:

How is ... diagnosed?:

How is ... treated?:

Emergency treatment for dogs with ketoacidois includes intravenous fluids and fast-acting insulin. Once the animal is stable, a regular regime of longer-acting insulin, diet, and exercise can be established.

For the veterinarian:

LABORATORY FINDINGS: fasting hyperglycemia with glucosuria; if the dog has ketoacidosis may see metabolic acidosis, hyponatremia, hyperkalemia, and hypochloremia.

Breeding advice:

FOR MORE INFORMATION ABOUT THIS DISORDER, PLEASE SEE YOUR VETERINARIAN.

Resources:

Nelson, R.W. 1995. Diabetes Mellitus. In S.J. Ettinger and E.C. Feldman (eds.). Textbook of Veterinary Internal Medicine, p. 1510-1537. W.B. Saunders Co., Toronto.