Botrina Dobermans | Thryoid function

The thyroid gland works in conjunction with the hypothalamus and pituitary glands. Together they release the right combination of hormones to control the body's metabolic rate. The major hormones are thyroxin (T4), triiodothyronine (T3) and thyrotropin (thyroid-stimulating hormone, TSH). These hormones circulate through the bloodstream and affect nearly every organ in the body. They play a major role in controlling metabolism in every cell of the body. Thyroxin is essential for the development of bones. The thyroid system greatly influences the immune system.

Hypothyroidism is the most common hormonal problem in dogs today and Dobermans have a higher than normal incidence. More than 70% of the 140 breeds recognized by the AKC are genetically predisposed to this condition. Scary? You bet! Hypothyroidism results when the thyroid gland does not secrete enough thyroxin. There are two types:

1. Naturally occurring or primary hypothyroidism, which has two causes:
a. Lymphocytic or autoimmune thyroiditis occurs when the body makes antibodies to fight against the thyroid gland, effectively destroying part of it. The thyroid gland then can not secrete enough thyroxin into the bloodstream. This is by far the most common cause of hypothyroidism.
b. Idiopathic thyroiditis. The cause is not known.

2. Secondary hypothyroidism, characterized by a lack of TSH. It is most commonly caused by an expanding, space-occupying tumour but it may also occur as a result of certain medications and some diseases such as diabetes mellitus, Cushing's Disease and heart disease.

Symptoms
Common symptoms of hypothyroidism include: hair loss, a change in skin and/or coat colour, strong smelling or greasy skin, lethargic behaviour (the dog won't run like it used to), always lying where it is very warm or hot, weight gain, mental dullness, development of fat deposits or ulcers on the eyes, alternating diarrhoea and constipation and vomiting. Intact bitches may have abnormal heat cycles, infertility or high puppy mortality; intact dogs may exhibit testicular atrophy or have low to no sperm count.

Treatment
Dogs diagnosed with hypothyroidism should be treated with a hormone replacement called levothyroxine. The medication is given every 12 hours for the life of the dog. The dog should have their blood checked regularly to ensure the dosage is correct and to permit timely adjustment to the dosage when needed.

Should breeders be testing for hypothyroidism? Absolutely! Should dogs with hypothyroidism be bred? Absolutely NOT!

All vertebrates (those species having a backbone) have a thyroid gland. It is located just caudal (behind) the larynx and adjacent to the trachea (windpipe). It has two lobes connected by a fibrous isthmus (band of tissue). The thyroid gland is extremely vascular. The thyroid gland is part of the Endocrine system. The Endocrine glands are a collection of glands that synthesize, store and release their secretions (hormones) directly into the bloodstream. They respond to changes in the internal and external environment to maintain homeostasis (a balance).

Physiology refers to the basic processes underlying the function and of the physical and chemical factors involved in the process.

Therefore: the role of the thyroid gland is to take iodine and convert it into the 2 main thyroid hormones; thyroxine(T4) and triiodothyronine(T3). T4 and T3 then circulate through the bloodstream and affect the metabolism of every cell in the body. The only difference between the two is that T4 has four iodine atoms attached to it and T3 only has three. Even though the thyroid gland secretes mostly T4(about 90%), it is T3 that is considered to be the active form of the hormone.

Conversion of T4 to T3 is a series of complex steps that involve mainly the liver and kidneys where T4 is stripped of an iodine atom and is converted to T3 when needed. One of the thyroid tests commonly ordered checks for the amount of circulating of “free” T4 and “free” T3. The bound thyroid hormone is transported by the blood to their target cells. Only unbound or “free” hormones are able to enter cells. This attachment process signals a receptor and activates the synthesis of various metabolic enzymes. These enzymes are what regulate the body's “set point” or “idling speed.” This basal metabolic rate governs the body's rate of oxygen consumption and energy expenditure, which in turn effects heat production. This is why we use up energy keeping warm and hypothyroid individuals and animals are cold intolerant.

To control the level of these hormones the hypothalamus and pituitary glands secrete compounds called releasing factors. In the case of the thyroid gland, they secrete a releasing factor called thyroid stimulating hormone (TSH). It is the amount of TSH circulating in the bloodstream that tells the thyroid gland how much thyroxin to secrete. In a very refined feedback mechanism between the hypothalamus, pituitary, and thyroid gland, the cells of the body get just the right amount of T4 and T3.

Thyroxin circulates throughout the bloodstream and affects almost all organs. It plays a major role in controlling metabolism, and is needed for growth. Thyroid hormones also stimulate mitochondrial oxygen consumption - that is synthesis at the cytoplasmic level; they also contain enzymes of the citric acid cycle and for fatty acid oxidation. Mitochondria also contain DNA, RNA, and ribosomes, replicating independently.

Impaired production and secretion of the thyroid hormones result in a decreased metabolic rate. This disorder called HYPOTHYOIDISM is most common in dogs but also affects humans and other large domestic animals.

Because the thyroid gland plays such a major role in regulation of the body, any disturbances in the thyroid system can cause serious problems in many of the body's other subsystems.

Control Mechanism

Thyroid hormones are not secreted at a continuous rate, but rather demonstrates the classical physiological example of negative feedback similar to a heating thermostat. Once levels of free circulating thyroid hormone have fallen to a certain plasma concentration, thyroid releasing hormone (TRH) is secreted by the hypothalamus. TRH in turn stimulates the release of thyroid stimulating hormone (TSH) from the anterior pituitary gland which “turns on” the synthesis of thyroid hormone. Another function of TSH is to maintain the structural integrity of the thyroid gland. Inadequate levels of TSH cause the thyroid gland to atrophy (decrease in size or wither up). Once the thyroid gland has atrophied, it cannot recover.

This is one reason why early diagnosis and intervention of thyroid disorders is so important.

Causes of Hypothyroidism

Primary (naturally occurring)

Primary hypothyroidism accounts for almost every case. It has two(2) main causes:

Lymphocytic thyroiditis

Also known as autoimmune thyroiditis, it occurs when the body makes antibodies against the thyroid gland. This effectively destroys part of it, so it has less thyroxin to secrete into the bloodstream. It is one of the most common causes of primary hypothyroidism.

This cause of hypothyroidism can start early in life. Symptoms will appear when it progresses to the point that the reserve power of thyroid gland is affected.

Idiopathic thyroiditis

In this form the cause is not scientifically known.

Secondary

Secondary hypothyroidism accounts for only a small percentage of cases. It arises when there is a lack of TSH, or secondary to some medications or diseases.

Miscellaneous

There are other causes of hypothyroidism that are encountered. Environmental toxins, nutritional (diet) deficiencies, allergies and exposure to chemical toxins are external factors that can trigger the onset of disease in the genetically susceptible animal.

Sometimes the same nutrient deficiencies that are causing hypothyroidism are also causing other disease conditions. By supplementing with the nutrients we know to be involved in thyroid hormone production, we may be able to correct the other health problems. (I'll go into that a little further on)

Gastrointestinal System

Diarrhoea, constipation and vomiting can occur in hypothyroid dogs.

Cardiovascular System

Abnormalities in heart strength, rate and rhythm, along with atherosclerosis could occur.

Arrhythmia's are usually diagnosed with an electrocardiogram (ECG).

Immune System

Inadequate thyroxin makes the immune system less effective at fighting infections, especially the bacterial skin infections (pyoderma) that occur secondarily. Suppression of the immune system might even increase susceptibility to demodex (a genus of parasitic mites within the hair follicles).

Hematologic System

Anemia is the most noted symptom. Anemia is not a disease but a sign of disease. It occurs when the red blood cells are low. There might also be a bleeding tendency, low white blood cells from bone marrow suppression, and low platelets.

Reproductive System

Breeding dogs might have abnormal heat cycles, infertility, and high puppy mortality.

Testicular atrophy and low sperm count, or no sperm count.

Endocrine System

In addition to low thyroxin, hypothyroidism is implicated in sugar diabetes (diabetes mellitus) and Addison's disease (hypoadrenocorticism).

Musculoskeletal System

Thyroxin is essential for the development of bones in young animals.

Hypothyroidism can occur at any age, although it tends to be a problem that affects middle aged to older dogs.

A thorough approach is needed for a correct diagnosis of hypothyroidism to rule out other diseases with similar symptoms such as Cushing's disease, skin allergies, sarcoptic mange, demodectic mange, and Ringworm.

Several canine breeds are prone to getting hypothyroidism:

Chow, Great Dane, Irish Wolfhound, Cocker Spaniel, Golden Retriever, Poodle, English bulldog, Schnauzer, Boxer, Dachshund, German Shepherd, Doberman Pinscher, Borzoi, Irish Setter, Old English Sheepdog, Miniature Schnauzer, Airedale terrier.

Females and males get it at about the same frequency. Neutered pets may be at a higher risk of hypothyroidism.

Routine physical exam findings might include:

ear problems
slow heart rate or abnormal heart rhythm
body temperature might be lower than normal
pale mucous membranes due to anemia
enlarged lymph nodes due to secondary bacterial infections
alopecia that is symmetrical
skin conditions in general

Diagnostic Tests

There is no one test that definitively diagnoses hypothyroidism except for a thyroid biopsy. There is also some controversy as to what tests are the best or most accurate in diagnosing.

A CBC (complete blood cell) and biochemistry panel will show the following on a hypothyroid dog. The CBC might show anemia or an elevated WBC (white blood cell count) where the anemia is due to thyroxin's direct effect on red blood cell production, the elevated white blood cell count (leukocytosis) is due to secondary bacterial infection.

Liver function tests might also be elevated, presumably from fatty changes that occur in the liver due to abnormal metabolism.

According to Dr. Jean Dodds, complete thyroid profiles need to be run and they are:

T3, T4, free T3, free T4, T3 and T4 auto antibodies, plus thyroglobulin auto antibody and TSH.

According to Long Beach Animal Hospital, they say that the most reliable test to confirm a diagnosis of hypothyroidism is TSH and that it eliminates some of the variables that suppress thyroxin production by the thyroid gland.

Once diagnosed, the treatment of choice is levothyroxine(T4) to be continued for the remainder of the dogs life. Levothyroxine has various trade names; Soloxine, Synthroid, Eltroxin.

Medication is given every 12 hours. A thyroid blood level needs to be checked initially after 1 month of treatment to make minor adjustments in dose. Thereafter, it should be checked every 6 months because as dogs age, so too does their body's' requirement for thyroxin change.

It is possible to overdose your dog with levothyroxine. Symptoms of overdose include excessive drinking and urination, restlessness and increased appetite. If these symptoms occur, get the dog in to the vet for a thyroid blood level check.

For those of you seeking to purchase a pet or show quality Doberman Pinscher, or any other breed, add this question to the list of questions to ask the breeder.

Thyroid function can break down for various reasons. This is a simple explanation of what can go wrong.

Thyroid hormone is made from a protein call TYROSINE. Tyrosine is made by converting phenalalinine, another protein, into tyrosine. This is done USING IRON. If iron is low, this will not occur.
Once Tyrosine is made, it goes to the thyroid gland. The mineral MANGANESE is then used to help convert Tyrosine into thyroxin. Thyroxin is also called T4. Iodine found in KELP is also involved.
Once Thyroxin is made, it goes to the liver. Some of it is set aside and is called reserve T4. In the liver, T4 is changed to T3. T3 is actually the hormone the body uses. This conversion is dependant on ZINC. Excessive levels of copper will interfere with this conversion.
Once converted to T3, the body can now use this hormone.
Once in the cell, the mineral SELENIUM helps the hormone work. Low levels of the mineral selenium will cause inactivity of the T3 hormone. SELENIUM also helps in the production of an enzyme that aids in the conversion of T4 to T3.

Diets LOW in protein and HIGH in fats can interfere with the thyroid function. Fat has been found to be antagonistic to thyroid function and lowers metabolism.

FATS AND OILS

Oils that can negatively affect thyroid health are those known as vegetable oils or polyunsaturated oils. The most common source of these oils is the soybean oil, or simply labeled vegetable oil. Polyunsaturated oils block thyroid hormone (T3) secretion. When the thyroid hormone is deficient, the body is exposed to increased levels of estrogen. The thyroid hormone is essential for making the “protective hormones - progesterone and pregnenolone”, so these hormones are lowered when anything interferes with the function of the thyroid. Polyunsaturated oils are made up of what is known as LONG CHAIN FATTY ACIDS - the kind of fatty acids that promote weight gain.

Coconut oil, on the other hand, is a saturated fat made up primarily of MEDIUM CHAIN fatty acids, also known as medium chain triglycerides (MCTs) and are known to increase metabolism and promote weight loss. Coconut oil can also raise basal body temperatures while increasing metabolism.

One of the reasons the long chain fatty acids in vegetable oils are so damaging to the thyroid is that they oxidize quickly and become rancid. The longer the long chain fatty acids are deposited in cells more often as rancid and oxidizing fat, impairment of the conversion of thyroid hormone T4 to T3 occurs, which is symptomatic of hypothyroidism. To create the enzymes needed to convert fats to energy, T4 MUST be converted to T3.

Coconut oil stimulates metabolism, is quickly metabolized and functions in some ways as an antioxidant. The liver is the main place where damage occurs from oxidized and rancid oils that cause cell membrane damage and the inability of the body to convert T4 to T3.

For decades we have known that LOW IODINE intake leads to low thyroid function. Iodized salt was intended to correct this problem, but it has not been the only answer. There are a number of foods known as goitrogens that block iodine. Two are : peanuts and peanut butter and SOYBEANS as vegetable protein and soybean oil.

Environmental stress such as chemical pollutants, pesticides, mercury, and fluoride are also tough on the thyroid. MERCURY may diminish thyroid function because it displaces the trace mineral SELENIUM and selenium is involved in conversion of thyroid hormones T4 to T3.

Since the thyroid makes a hormone called calcitonin that allows for absorption of calcium, taking thyroid hormone replacement drugs WON’T fix the underlying problem and calcium absorption will be impaired.

HOW TO CORRECT A THYROID PROBLEM or prevent one :

A number of nutrients have been shown to contribute to thyroid health: they include: ZINC, SELENIUM, B VITAMINS, VITAMIN C, VITAMIN E, VITAMIN A, BETA CAROTENE, IODINE.

Iodine is most abundant in sea vegetables, fish, seafood, and eggs. Kelp powder in place of salt. More fish, especially the smaller coldwater fish such as SALMON (avoid farm raised), MACKEREL, HALIBUT, SOLE, SNAPPER. Avoid tuna and swordfish as they tend to be higher in mercury. If hypothyroidism is already present, add beta carotene to Vitamin A as hypothyroidism affected people and dogs don’t have the ability to convert beta carotene to Vitamin A. SELENIUM is involved in conversion of T4 to T3 and low selenium levels could lead to low T3 levels. Mercury will displace selenium, so it is a good idea to have a liver enzyme panel done to detect high levels of copper and mercury.

A sulphur compound found in the RADISH is a regulator of thyroxine and calcitonin.

What I do as a preventative is :

juice carrots, cucumber, celery, radishes, lemon. Add a dash of powdered Ultra Kelp for a boost of iodine.

AVOID: TURNIPS, CABBAGE, MUSTARD, CASSAVA ROOT, PINE NUTS, MILLET, PEANUTS, AND SOYBEANS, PEANUT BUTTER.

OMIT ALL SUGARS, REFINED GRAINS, HYDROGENATED and partially hydrogenated oils.

EXERCISE.

Of the major vitamins, some are water-soluble and some are oil-soluble. Water-soluble vitamins must be taken into the body daily, as they can’t be stored and are excreted within one to 4 days. These include: vitamin C (250mg - 1000mg), the B-complex vitamins (50) is sufficient.

Oil-soluble vitamins can be stored for longer periods of time in the body’s fatty tissue and the liver. These include: vitamins A, D, E and K.

Essentials minerals needed are: chromium, iron, zinc, manganese, selenium. Calcium and magnesium in low amounts.

Calcium: is essential to heart health, nerves, muscles and skin.

Chromium: is a mineral that becomes a part of the glucose tolerance factor (GTF), and aids in insulin utilization and blood sugar control

Beta Carotene: widely accepted as a cancer preventative. Is found in leafy green vegetables such as Swiss chard - cooked the dogs love it chopped up (I also add the water it’s cooked in to add to their food)

Iron: an essential mineral prevents anemia and transports oxygen through the body.

Magnesium: an essential mineral maintains the electrical potential across nerve and muscle membranes. Is essential for proper heart beat and nerve transmission. Is closely related to calcium and phosphorus in body function.

Manganese: is essential to several critical enzymes necessary for energy production, bone and blood formation, nerve function and protein metabolism. Is involved in the metabolism if fats and glucose, AND it allows the body to use thiamine and Vitamin E.

Selenium: essential primarily in enzymes that are antioxidants. Involved in THYROID hormone production, is essential in lowering risk of several types of cancer. In combination with Vitamin E, selenium AIDS THE PRODUCTION OF ANTIBODIES AND HELPS MAINTAIN A HEALTHY HEART. It also aids in the function of the pancreas.

Vitamin C: as an antioxidant, it inhibits formation of nitrosamines (a suspected carcinogen). Vitamin C is important for maintenance of bones, teeth, collagen and blood vessels, ENHANCES IRON ABSORPTION and red blood cell formation, helps in the utilization of carbohydrates and synthesis of fats and proteins, aids in fighting bacterial infections, and interacts with other nutrients.

Vitamin E: an essential fat-soluble vitamin. Helps protect cell membranes, lipoproteins, fats and vitamin A from destructive oxidation. Helps protect red blood cells.

Zinc: the functions of zinc are enzymatic. Zinc is a constituent of insulin and male reproductive fluids. Is involved in the health of the IMMUNE SYSTEM, and assists with Vitamin A utilization.

Capsaicin: (found in cayenne pepper, chillis) & Ginseng STIMULATE THE THYROID.

Be aware : that low levels of molybdenum, zinc, manganese in soils and food increases absorption of copper. Increased cadmium in soil and foods increases copper retention. Antifungal sprays used on vegetables increase copper retention.