Hyperadrenocorticism (Cushing's Disease)
Cushing's disease is caused by chronic excess cortisol in the blood. This excess of cortisol can cause problems with many body systems, although, in some dogs, only one or a few clinical signs may predominate. It is very important to have annual (or biannual if older animal) tests performed to screen for this disease (and many others). Like many diseases, if caught early, your pet can avoid long-term side effects of the disease.
Causes:
- Pituitary Dependent Hyperadrenocorticism: - This is the most common cause of naturally occurring Cushing's disease in dogs accounting for 85% of all cases. Most of the time this type is benign, but it can cause neurologic signs if the pituitary gets too large. This type sends a hormonal signal to both adrenal glands causing the glands to enlarge and produce too much cortisol.
- Cortisol-Secreting Adrenocortical Tumor: - These tumors are responsible for about 15% of dogs with naturally occurring Cushing's disease. About 50% of these tumors are benign, and 50% are malignant. With this type of hyperadrenocoricism, only one adrenal gland is affected. It will enlarge, and the opposite adrenal gland, compromised of non-cancerous cells, atrophies (or decreases in size).
- Iatrogentic Hyperadrenocorticism: - This type is caused by excessive or prolonged corticosteroid administration leading to atrophy of both adrenal cortices. This is usually caused by excessive steroid administration to control allergic or immune-mediated disorders. It can also develop as a result of chronic administration of eye, ear, or skin medications containing glucocorticoids.
Clinical Signs: - General Appearance and Behavior:
- Pendulous, distended, or "pot-bellied" appearance
- Hair loss
- Muscle atrophy
- Weakness
- Lethargy
- Depression
- Dermatologic:
- Hair loss
- Poor hair regrowth
- Thin skin
- Bruises easily
- Poor wound healing
- Increased pigmentation of skin
- Calcinosis Cutis (hard deposits in skin)
- Urinary:
- Drinking excessive amounts of water
- Urinating frequently
- Urinary tract infections common (may see blood in urine, may strain to urinate, may feel urge to urinate frequently)
- Reproductive:
- Testicular atrophy
- Female infertility
- Respiratory:
- Excessive panting
- Thromboembolism (Blood Clots) can lead to respiratory distress and can be fataEndocrine:
- Some dogs may develop diabetes mellitus
- Neuromuscular:
- Lethargy
- Circling
- Seizures
- Beharioral changes
- Depression
- Muscle wasting
- Muscle weakness
- GastrointesTinal:
- Excessive food comsumption (polyphagia)
- Enlarged liver
- Pancreatitis
- Ocular:
- Corneal ulcerations
- Corneal clacification
- Cataracts
- Lipemia retinalis
- Lesions associated with systemic hypertention
- KCS
- Cardiovascular:
- Systemic hypertension
- Thromboembolism
- Susceptibility to bruising
- Heart murmur
Diagnosis:
Based upon clinical signs and blood tests performed by your veterinarian.
Treatment:
Usually involves treatment with an oral medication in which a loading dose is given initially, a blood test is performed as a recheck, and maintenance therapy is continued for life. Recheck appointments will be required occasionally to make sure your pet is taking the correct maintenance dose. These appointments are necessary, since an overdose of medication can be harmful to your pet.
Hypothyroidism:
Hypothyridism is a very common disease in dogs affecting
virtually every body system. It occurs predominantly in middle-aged, pure-breed dogs, but dogs of any age or mixed-breed dogs may be affected, also. (Hypothyroidism is rare in cats.) It is a disorder in which too little thyroid hormone is in circulation which impairs cellular metabolic activity. This results is a wide array of clinical signs.
Your pet may not show or develop every symptom. Clinical signs
develop slowly and are
progressive. It is essential to treat the disease so your pet may have a longer, healthier, happier life.
Causes:
- Primary Hypothyroidism - The vast majority of hypothyrid dogs are affected with primary hypothyroidism. This results from the gradual destruction of the thyroid gland.
- Lymphycytic Thyroiditis
- Idiopathic Atrophy of the Thyroid Gland
- Cause is unknown.
- Adipose (fat) tissue replaces the thyroid parenchyma without inflammation.
- Uncommon causes of Primary Hypothyroidism:
- Congenital Hypothyroidism
- Neoplasia (Cancer)
- Surgical removal of the Thyroid Gland
- Radioiodine Treatment
- Iodine deficiency
- Secondary Hypothyroidism - Impaired secretion of thyroid-stimulating hormone (TSH)
- Pituitary Tumors
- Suppression of Thyroid Function by Hormones or Drugs (usually steroids)
- Pituitary Suppression from Hyperadrenocorticism (Cushing's disease)
- Euthyroid Sick Syndrome - Suppression of thyroid hormone from concurrent illness
- Cystic Rathke Pouch
- Tertiary Hypothyroidism - Deficient production or release of thyrotropin-releasing hormone (TRH); NOT yet reported in dogs.
Clinical Signs:
- General Appearance and Behavior:
- Weight gain
- Lethargy / Inactivity
- Exercise Intolerance
- Mentall Dullness
- Cold Intolerance
- Generalized Weakness
- Hypothyroid animals do not metabolize drugs as well; anesthetic agents have a more potent and longer-lasting effect.
- Dermatologic:
- Excessive scaling / dry skin
- Greasy skin possible
- Excessive shedding
- Lack of Hair Regrowth following Clipping
- Dry or Lusterless Haircoat
- "Rat Tail" appearance
- Hair may be lighter in color, look frizzy or brittle
- Hyperpigmentation (Darkening of Skin)
- Thickening of Skin
- "Tragic" facial expression due to accumulation of mucopolysaccharides in skin
- Recurrent Skin Infections
- Recurrent otitis externa (ear infections)
- Comedones (Blackheads)
- Cardiovascular:
- Decreased Heart Rate
- Decrease Contractility of Heart
- Hematologic:
- Anemia
- Hyperlipidemia (High blood fats) / High Cholesterol
- Coagulopathy (Blood Clotting diseases)
- Reproductive:
- Galactorrhea - excessive or spontaneous milk flow in intact female
- Infertility
- Abortion
- Lack of Libido
- Ocular:
- Loss of Vision
- Lipid Deposits in Cornea
- Corneal Dystrophy
- Corneal Ulcers
- KCS - "Dry eye"
- Anterior Uveitis
- Glaucoma
- Retinopathies
- Gastrointestinal:
- Immunologic:
- Neuromuscular:
- Generalized Weakness
- Incoordination
- Head Tilt
- Facial Paralysis
- Circling
- Knuckling
- Seizures
- May be linked to laryngeal paralysis, megaesophagus, and Horner's syndrome
- Congenital Hypothyroidism:
- Dwarfism
- Shortened Mandible
- Protruding Tongue
- Delayed Dental Eruption
Diagnosis:
- Based upon clinical signs and blood tests performed by your veterinarian.
Treatment:
- Consists of daily administration of thyroid hormone supplementation.
- Response to therapy does not occur overnight. It takes time for hormone concentrations to reach peak levels and for the body to respond to the change.
- An improvement in attitude, an increase in activity, muscle strength, and appetite is usually noted in 1-2 weeks.
- Beginning of resolution of neurologic signs and weight loss may take 1-4 weeks.
- Dermatologic signs may require at least a month to begin to resolve, but they may take a longer period to see any effect. It may take several months for complete hair regrowth.
- Your dog will need to be rechecked by your veterinarian periodically to make sure the correct therapeutic level is achieved.
