Endocrine diseases of dogs

Hypothyroidism is a fairly common disease of the endocrine system in dogs. It is most often an acquired disease caused by immune-mediated damage or idiopathic ( reason unknown) atrophy of the thyroid gland. There are other causes of hypothyroidism (neoplasia of the thyroid gland or hypothalamus, infections, iodine deficiency, medications), but they are extremely rare. Hypothyroidism significantly lowers T4 level in blood; can be primary (i.e., problem comes directly from the thyroid gland, which is unable to produce T4 hormone (95% of cases), secondary to problems in the hypothalamus when thyroid stimulation is impaired (very rare) or congenital (also very rare). The average age of occurrence of disease is 7 years. Dogs of large breeds (Golden Retrievers, Dobermans, German Dogs, Irish Setters) are more susceptible, but there is a predisposition in small breeds (cocker spaniels, miniature Schnauzers, dachshunds, poodles). However, note that hypothyroidism can develop in any middle-aged dog. 

The most common symptoms of hypothyroidism are lethargy (dogs become more lethargic, sad), weight gain and the appearance of symmetrical alopecia (baldness). The latter may be accompanied by pyoderma (inflammation of the skin). Diagnosis includes a detailed anamnesis and examination, a general blood test and T4 (these two tests are performed locally), and TSH hormone (sent to Laboklin, Germany). 

Treatment of hypothyroidism consists of medication to increase the T4 hormone in the blood. Treatment is lifelong and requires periodic monitoring. Progress is clearly visible and comes quite quickly. Dogs become active, alopecia gradually disappears, the quality of skin and coat significantly improves, weight returns to normal. 

Cushing’s disease (hyperadrenocorticism) is another common endocrine disease in dogs. The most common cause is bilateral adrenal hyperplasia caused by a neoplasm or hyperplasia of the pituitary gland (80-85% of cases). Less commonly, it can be caused by a neoplasm in the adrenal gland itself. In about half of the cases, the neoplasm is malignant. Prolonged use of corticosteroid medications (for example, to control allergies) may also be the cause. Hyperadrenocorticism significantly increases the level of cortisol in the blood, which leads to the disruption of the entire body. 

The main symptoms of Cushing’s disease are polyuria, polydipsia, and polyphagia, which is manifested by frequent and abundant urination and increased water and food intake. You can also observe a significant  increase size of the belly , the coat becomes dull, sparse. Skin problems, weight gain, weakness, etc. may occur. Diagnosis includes a detailed anamnesis and examination, general blood test, biochemical blood test, urinalysis, abdominal ultrasound, ACTH (adrenocorticotropic hormone) stimulation test – all performed locally, and cortisol blood level analysis (performed in a laboratory in Tallinn, results arrive within 1-2 days). 

Depending on the etiology of the disease, treatment can be surgical or medical.  In the case of a tumor process in one adrenal gland, adrenectomy, i.e. removal of the damaged adrenal gland, can be considered. If we are dealing with so-called central hyperadrenocorticism (i.e. the root cause is in the pituitary gland), treatment involves the lifelong use of encapsulated drugs and periodic monitoring. If the disease was provoked by prolonged use of corticosteroid drugs, then the only treatment is to cancel these drugs. 

Since Cushing’s disease is central in most cases, you most often have to choose lifelong medication (unfortunately quite expensive). The prediction, however, is very favorable. If you follow all the recommendations of the doctor, as well as in the absence of complications and concomitant diseases, improvements occur quite quickly. The appetite returns to normal, frequent urination and copious fluid intake disappear, the quality of the coat improves, and skin problems are resolved. However, it should be noted that in the treatment of hyperadrenocorticism, periodic monitoring of the level of cortisol in the blood is extremely important; with uncontrolled treatment, the reverse pathology can develop – hypoadrenocorticism or Addison’s disease,which can be deadly.