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Hypothyroidism
What is Hypothyroidism?
Hypothyroidism is an underactivity of the
thyroid gland resulting in too little production of thyroid hormone known as thyroxin
which is an iodine-containing substance which helps control the body's metabolism
(ie.
rate at which food is converted into energy).
The thyroid gland is an endocrine gland
located in front of
and on both sides of the lower throat just below the level of the Adam's apple. Its only
known function is to synthesize the thyroid hormone. However, the thyroid gland is
influenced by the pituitary gland which produces a thyroid- stimulating hormone
(TSH, thyrotopin), but the pituitary gland itself is stimulated by a hormone produced in the
hypothalamic area of the brain.
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Known Causes
Hypothyroidism may therefore be caused not only by a disorder
of the thyroid gland itself , but also by a variety of diseases that affect the
hypothalamus and pituitary gland. Hashimoto's disease, or chronic lymphocytic thyroiditis
(inflammation of the thyroid), is the most common cause in the U.K.
An Iodine deficient diet can also cause hypothyroidism as
can surgery and drugs (e.g. iodides, lithium, phenylbutazone), and it may also be caused
congenitally. Idiopathic (cause unknown) hypothyroidism is believed to be a disease of the
immune system and is associated with underactivity of other endocrine glands and immune
disorders such as systemic lupus, erythematosis and rheumatoid arthritis.
Adult Hypothyroidism: -The symptoms of adult onset
hypothyroidism result from an overall slowing of body metabolism. The onset is usually
gradual and, in most instances, the person may not recognize the early signs and symptoms
which include: fatigue, lack of energy, intolerance of cold temperatures, constipation,
heavy menstrual periods, and weight gain despite a diminishing appetite. Often these
symptoms are attributed to other conditions such as stress, depression, or overwork, but
the symptoms worsen as time passes and become more obvious: the pulse slows and weakens;
the skin becomes cool, dry, coarse, and doughy; muscles ache; there is puffiness around
the eyes; hair falls out; the voice becomes hoarse; and the reflexes are sluggish. Changes
in mood and personality simulating psychiatric illness may be the most salient features.
In some cases, the thyroid gland enlarges to produce a visible bulge or goitre in the
neck. Large goiters can cause difficulty swallowing. Advanced hypothyroidism is also known
as myxedema. If treatment is not initiated, or if infection, severe stress, surgery, or
medications aggravate the condition, the patient may slip into life-threatening myxedema
coma.
Childhood Hypothyroidism: - Untreated hypothyroidism that
begins at birth or in early childhood is referred to as cretinism. It is characterized by
growth failure, delayed mental development, unusual facial features, and feeding
difficulties, as well as many of the features of the adult condition. School age children
may experience a delay in puberty and have difficulty with their studies.
Evaluation & Diagnosis: - Hypothyroidsim is often not
diagnosed in the early stages because the signs and symptoms in adults are initially
nonspecific but an alert physician will always consider it in cases of chronic fatigue,
obesity, psychiatric disturbances, and developmental abnormalities. The diagnosis is
confirmed by measurement of blood levels of thyroid hormone and TSH. In the rare cases of
pituitary or hypothalamic hypothyroidism, special hormone stimulation tests are necessary
and other concurrent hormone deficiencies must be ruled out. Newborn babies are routinely
screened for this condition in order to prevent permanent damage related to cretinism.
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Conventional Treatment
Medical treatment is most commonly an orally administered,
synthetic preparation of L-thryoxine (Synthroid). In order not to "shock" the
system or aggravate co-existing heart disease in older persons, the drug is first
administered in small doses and gradually increased over a period of several months. The
proper maintenance dose is determined individually by measuring blood hormone levels. In
patients with cretinism, the rate of replacement is crucial to avert further developmental
delay. Myxedema coma, an often fatal condition, requires prompt emergency therapy.
In some cases the thyroid is completely destroyed with
radioactive iodine or surgically removed to make the prescription of Synthroid easier to
determine. It is important to realise that all forms of medically treated hypothyroidism
necessitate lifelong drug therapy which is not without side effects including arrhythmias,
anginal pain, headaches, sweating, nausea, muscular cramps and restlessness.
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