The thyroid
The thyroid gland produce and store thyroxine (T3) and Trijodthyroxin (T4). By the secretion of these hormones affect the glands very comprehensive on metabolism, organ development, growth, and parts of the nervous system on one. The T4 provides a reservoir for the conversion to the active T3 is that in which its meaning is not clarified in the dog.
Thyroid hormone production and size are two overarching control systems controlled by:
The pituitary gland (hypophysis), throwing the mood enhancing thyroid-stimulating hormone (TSH).The less T3 in the blood, the more TSH is released to the production ramp up.
The Hypopyhse in turn is a part of the forebrain regulated by, hypothalamus, TRH, the Threotropin-releasing hormone distributes the:
Overactive thyroid (hyperthyroidism)
The increased hormone production causes a general increase in metabolism. Sie wird beim Hund relativ selten beobachtet und tritt dann überwiegend im Zusammenhang mit Schilddrüsenkarzinomen auf. It is relatively rarely observed in the dog and then enters mainly in connection with thyroid cancer. Allerdings kann sie auch als Durchgangstadium zu Beginn einer Unterfunktion der Schilddrüsen beobachtet werden. However, they can transition stage at the beginning of an under-active thyroid can be observed as well. Here is a high probability to autoimmune diseases, ie the immune system is abnormal manner) against its own thyroid tissue from (.
Under-active thyroid (hypothyroidism)
Causes:
Acquired hypothyroidism
- By lack of iodine in the diet
- Virus Diseases
Congenital (inborn) hypothyroidism
It shows serious diseases, such as growth disorders.
If there is a thyroid function during embryonic development, this leads to cretinism with mental retardation and a retardation of sexual development.Other features are a short, kyphoischer back, a squat neck, thick and short front legs, a slender hind legs, a deep chest and the sad sight.
Other causes are congenital thyroid abnormalities in the "higher" control units of the observed. These abnormalities in pituitary or hypothalamus but are very rare in dogs and should find mention here for completeness only.
In the case of congenital malformations have a genetic predisposition is very likely.
Hypothreose the adult dog
primary hypothyroidism
The thyroid gland itself can not produce enough hormone. Although this form of Hypothreose is common, remain a lack of diagnostic facilities many cases undetected due or are being treated wrong. As causes, one finds:
Autoimmunerkrankung Autoimmune disease
idiopathic atrophy (in German: Tissue shrinkage of unknown cause), this first make two of about 95% of all Hypothreosen!
Inflammation
Tumors
congenital thyroid dysfunction
State after thyroid surgery
after radiation treatment of thyroid
Medikamtenteneinwirkung
Extreme iodine deficiency
severe hormone loss via kidney or intestine.
If the people are significantly more of the female gender of hypothyroidism is also affected (10:1), so the ratio female: male in dogs at 2.5: are first
On the first two forms of primary hypothyroidism, I would like to focus:
Autoimmune thyroiditis:
In humans, this disease is the most common cause of primary hypothyroidism dar. Over 90% of the cases involve women. Besides the signs, the goiter.
Triggered by this disease is that the body's immune system regards the thyroid tissue.
In the blood, there are antibodies against thyroid tissue and colloid (the reserve deposit for SD-hormones). Result is a shrinkage or even an enlargement of the tissue, the normal hormone production, may be reduced or even overshoots. There is a chronic inflammation of the thyroid gland, more and more cells are destroyed. This hormone is produced less and less. Final state after atrophy (the loss) the aplasia (absence) of the thyroid.
Even the dog disease mechanism is the same. However, blood is the antibody level in the not so meaningful as in humans, so that the diagnosis more difficult here. Also be found in dogs no goiter.
It is believed that the occurrence of these factors cause disease Gentet.This is also suggested the existence of this disease is more common in other autoimmune diseases also occur: diabetes mellitus, anemias, vascular diseases, chronic rheumatism and others.
Idiopathic atrophy of the thyroid tissue:
By a non-inflammatory process leads to a progressive loss of tissue and to a thyroid shrinkage. Here again, genetic factors are likely the cause.
Secondary Hypothreose
The failure of TSH is produced at a low T4. As there are causes diseases of the pituitary gland, such as congenital malformation of the pituitary gland or tumorous processes.This form occurs in dogs less than 5% of the cases in front.
Tertiary hypothyroidism
The outbreak is located in the hypothalamus, the distribution of TRH the Prodution of TSH in the controls by Hypopyhse. This form of disease has never been described in domestic animals.
The symptoms
Since the institutions have high reserve capacity, sub-functions are also thyroid only noticed when about 75% of Schilddrüsenngewebes have failed. Therefore, it can take two to three years until the disease breaks out.As the disease progresses slowly but rather, it often happens that the dog four to six years to be investigated first. In many dog owners also think that their pet altered by simply getting older. If left untreated, there is the entire clinical picture over a longer period in first. Since thyroid hormones affect all body cells, is in a disease with many symptoms to be expected:
As a general symptoms may occur:
Lethargy, lack of interest, increased need for sleep, decreased endurance: a youngish dog suddenly seems very old.
sad facial expression
painful swallowing
Personality changes (irritability, aggressiveness)
Sensitivity to cold
puffy face
Weight gain for the same amount of food
Lameness
At the cardiovascular system, one finds:
decreased heart rate
weak pulse
Lowered body temperature
cold skin
Skin:
dry, brittle, dull hair coat
Shed
premature graying
Hair loss
Hyperpigmentation of the skin
"Afghanenrute"
delayed molt
Prepared by the Rhodesian Ridgeback breeders:
Mashambani
& Mhangura
