What is Hypothyroidism?

Hypothyroidism is the condition in which the thyroid is underactive (i.e., it is producing an insufficient amount of thyroid hormones). Hypothyroidism is the most common thyroid disorder. Severe hypothyroidism can lead to a condition called myxedema, characterized by dry, thickened skin and course facial features.

Symptoms of low thyroid function include:

·    Fatigue, exhaustion, feeling run down, sluggish, lethargic
·    Depression, restlessness, moods swings, feelings of sadness, feelings of worthlessness
·    Loss of interest in normal daily activities
·    Poor concentration, poor memory
·    An enlarged thyroid gland (goiter).
·    Modest weight gain, often 10 lb or less.
·    Swelling of the arms, hands, legs, and feet, and facial puffiness, particularly around the eyes.
·    Hoarseness.
·    Muscle aches and cramps.

What causes hypothyroidism?
Hypothyroidism occurs when the thyroid gland fails to produce enough thyroid hormone. Without enough thyroid hormone, the body becomes tired and run down. Every organ system slows, including the brain, which affects concentration; the gut, causing constipation; and metabolism -- the rate at which the body burns energy -- resulting in weight gain. Although there are many different causes of hypothyroidism, the resulting effect on the body is the same.

The most common cause of hypothyroidism is an autoimmune disease called Hashimoto’s thyroiditis. Normally, antibodies produced by the immune system help protect the body against viruses, bacteria and other foreign substances. With Hashimoto’s thyroiditis, antibodies attack the thyroid and keep it from producing enough hormone.

GRADES OF HYPOTHYROIDISM
Hypothyroidism is a graded phenomenon, ranging from very mild cases in which biochemical abnormalities are present but the individual hardly notices symptoms and signs of thyroid hormone deficiency, to very severe cases in which the danger exists to slide down into a life-threatening myxedema coma. In the development of primary hypothyroidism, the transition from the euthyroid to the hypothyroid state is first detected by a slightly elevated serum TSH, caused by a minor decrease in thyroidal secretion of T4 which doesn't give rise to subnormal serum T4 concentrations.

Diagnostic testing
To diagnose primary hypothyroidism, many doctors simply measure the amount of Thyroid-stimulating hormone (TSH) being produced. High levels of TSH indicate that the thyroid is not producing sufficient levels of Thyroid hormone (mainly as thyroxine (T4) and smaller amounts of triiodothyronine (fT3)).
·    thyroid-stimulating hormone (TSH)
* free triiodothyronine (fT3)
* free levothyroxine (fT4)
* total T3
* total T4

Manifestations of Hypothyroidism
Hypothyroidism is a classical disease with a classical collection of clinical signs. One particularly well published survey of 162 confirmed hypothyroid dogs showed the following common findings:
·    88% had some kind of skin abnormality
·    40% had hair loss (often this starts on the tail leading to a "rat tail" appearance or a bald area around the collar is created)
·    22% had skin infection (often dogs are scaly and smelly due to an excessively oily coat)

Hypothyroidism in children
One in 4,000 babies is born with congenital hypothyroidism. In about five per cent of cases, there's a genetic dysfunction in hormone production.
Children with acquired hypothyroidism may have other autoimmune disorders including diabetes mellitus. Both are more common in children with Down's syndrome or Turner syndrome. It's more common in girls than in boys.