THYROID GLAND and THYROXINE
Oct 15, 2009 6:59:12 GMT 10
Post by Tom Meulman on Oct 15, 2009 6:59:12 GMT 10
THYROID GLAND and THYROXINE
The principal function of THYROID HORMONE (THYROXINE) is to control and stimulate the rate of metabolism of the body
When levels of THYROXINE are decreased it results in decreased physical and mental vigour.
FACTORS INFLUENCING THE FUNCTION OF THE THYROID
Iodine Metabolism
Iodine is essential to the production of Thyroxine and is the only known function of iodine in the body.
Thyroid Stimulating Hormone (TSH)
A hormone produced by the pituitary gland stimulates activity of the thyroid gland by increasing the uptake of iodide, and stimulating its conversion into Thyroxine.
Thyroid Binding Globulin (TBG)
Serum proteins that act as carrier agents for Thyroxine and distribute it throughout the body.
Anything that affects the IODIDE metabolism, the production of TSH, or the binding of Thyroxine to GLOBULIN, affects the function of Thyroxine in the body.
Hyperadrenocorticism (Stress)
This causes a rapid decrease in TSH (thyroid stimulating hormone), greyhounds suffering this condition are often HYPOTHYROID. (Low serum Thyroxine)
Anabolic Steroids
These decrease the levels of available TBG (Thyroxine binding globulin) and so reduce the level of Thyroxine in the body.
There is also a genetic factor involved in thyroid function, in animals where it exists; much of the body iodide is not available for Thyroxine production.
LOW PLASMA THYROXINE
Demonstrated by a test to determine the globulin bound level of Thyroxine (T4) or a test to determine the level of Thyroxine not bound to globulin (free T4), is extremely common in the racing greyhound, in many cases this may be due to severe stress.
Generally treatment consists of providing oral supplements of THYROXINE SODIUM.
The initial dose should be small, and increases made at 14-day intervals until the desired metabolic balance is achieved.
At this time it may also be worthwhile to provide the dog with extra iodine in the diet, by adding a pinch of iodised salt to the main meal each day.
Iodine may also be given as a supplement: 2 drops of 2.5% Iodine in a cup of low fat milk, given as a drink every third day for 5 doses.
Adverse Reactions
Some dangers exist in providing excessive doses of oral Thyroxine in an attempt to rapidly increase thyroid hormone levels.
Administration of Thyroxine further depresses TSH production, possibly compounding the original cause.
Excess levels of Thyroxine may lead to heart muscle damage, and or bone fractures.
A single dose may take up to a week to develop its maximum response, and repeated daily doses may have a cumulative effect, which does not become fully apparent for 14 day’s or more.
The initial dose should be small, usually 100 microgram daily, and increases made at fortnightly intervals by 50 microgram until the correct metabolic balance is achieved.
Overdose may cause restlessness, increased excitability and the possibility of heart muscle damage during strenuous exercise.
As well as supplementing the thyroid hormone levels with Thyroxine sodium, every effort should be made to rectify the training program and reduce the stress levels.
PARATHYROID HORMONE (PTH)
Small glands that are attached to the thyroid gland produce PTH.
PTH acts in conjunction with other hormones to control the CALCIUM and PHOSPHATE levels in the body.
When calcium intake is insufficient, it elevates the serum calcium level by dissolving CALCIUM SALTS in the bone and increasing the excretion of PHOSPHORUS.
The primary function of the PARATHYROID HORMONE is to maintain the concentration of IONISED CALCIUM in the plasma within a narrow range, in spite of wide variations in CALCIUM intake.
The principal function of THYROID HORMONE (THYROXINE) is to control and stimulate the rate of metabolism of the body
When levels of THYROXINE are decreased it results in decreased physical and mental vigour.
FACTORS INFLUENCING THE FUNCTION OF THE THYROID
Iodine Metabolism
Iodine is essential to the production of Thyroxine and is the only known function of iodine in the body.
Thyroid Stimulating Hormone (TSH)
A hormone produced by the pituitary gland stimulates activity of the thyroid gland by increasing the uptake of iodide, and stimulating its conversion into Thyroxine.
Thyroid Binding Globulin (TBG)
Serum proteins that act as carrier agents for Thyroxine and distribute it throughout the body.
Anything that affects the IODIDE metabolism, the production of TSH, or the binding of Thyroxine to GLOBULIN, affects the function of Thyroxine in the body.
Hyperadrenocorticism (Stress)
This causes a rapid decrease in TSH (thyroid stimulating hormone), greyhounds suffering this condition are often HYPOTHYROID. (Low serum Thyroxine)
Anabolic Steroids
These decrease the levels of available TBG (Thyroxine binding globulin) and so reduce the level of Thyroxine in the body.
There is also a genetic factor involved in thyroid function, in animals where it exists; much of the body iodide is not available for Thyroxine production.
LOW PLASMA THYROXINE
Demonstrated by a test to determine the globulin bound level of Thyroxine (T4) or a test to determine the level of Thyroxine not bound to globulin (free T4), is extremely common in the racing greyhound, in many cases this may be due to severe stress.
Generally treatment consists of providing oral supplements of THYROXINE SODIUM.
The initial dose should be small, and increases made at 14-day intervals until the desired metabolic balance is achieved.
At this time it may also be worthwhile to provide the dog with extra iodine in the diet, by adding a pinch of iodised salt to the main meal each day.
Iodine may also be given as a supplement: 2 drops of 2.5% Iodine in a cup of low fat milk, given as a drink every third day for 5 doses.
Adverse Reactions
Some dangers exist in providing excessive doses of oral Thyroxine in an attempt to rapidly increase thyroid hormone levels.
Administration of Thyroxine further depresses TSH production, possibly compounding the original cause.
Excess levels of Thyroxine may lead to heart muscle damage, and or bone fractures.
A single dose may take up to a week to develop its maximum response, and repeated daily doses may have a cumulative effect, which does not become fully apparent for 14 day’s or more.
The initial dose should be small, usually 100 microgram daily, and increases made at fortnightly intervals by 50 microgram until the correct metabolic balance is achieved.
Overdose may cause restlessness, increased excitability and the possibility of heart muscle damage during strenuous exercise.
As well as supplementing the thyroid hormone levels with Thyroxine sodium, every effort should be made to rectify the training program and reduce the stress levels.
PARATHYROID HORMONE (PTH)
Small glands that are attached to the thyroid gland produce PTH.
PTH acts in conjunction with other hormones to control the CALCIUM and PHOSPHATE levels in the body.
When calcium intake is insufficient, it elevates the serum calcium level by dissolving CALCIUM SALTS in the bone and increasing the excretion of PHOSPHORUS.
The primary function of the PARATHYROID HORMONE is to maintain the concentration of IONISED CALCIUM in the plasma within a narrow range, in spite of wide variations in CALCIUM intake.