Hypothyroidism

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Hypothyroidism is a pathologic state caused by insufficient secretion of thyroid hormones by the thyroid gland. There are several distinct causes for chronic hypothyroidism, most common being Hashimoto's thyroiditis and iatrogenic (or postoperative) hypothyroidism following radioiodine therapy for hyperthyroidism.

The severity of hypothyroidism varies widely. Some patients are classified as subclinical hypothyroid when only diagnostic findings show thyroid hormone abnormality. Others have moderate symptoms that can be mistaken for other diseases and states. Advanced hypothyroidism is easily recognized even for non-specialist.

Contents

1 Signs and symptoms

2 Neonatal period

3 Hashimoto's thyroiditis

Signs and symptoms

Slowed speech and impaired memory
Cold intolerance
A slow heart rate and sluggish reflexes
Dry puffy skin and hair loss
Can contribute to depression
May lead to weight gain

In the elderly, hypothyroidism is relatively common and can be easily missed. It is an important but treatable cause of depression in this age group.

Neonatal period

Thyroid hormone is very important to neural development in the neonatal period. A deficiency of thyroid hormones can lead to cretinism. For this reason it is important to detect and treat thyroid deficiency early. In Australia and many other countries this is done by testing for TSH on the routine neonatal heel pricks performed by law on all new born babies.

Hashimoto's thyroiditis

Sometimes called Hashimoto's Disease, this is part of the spectrum of auto-immune diseases and is related to Graves' disease, lymphocytic thyroiditis as well as other organ related auto-immune conditions such as Addison's disease, diabetes, premature menopause and vitiligo. Hashimoto's is a lymphocytic and plasmacytic thyroid inflammation that eventually destroys the thyroid. Patients require permanent thyroid replacement.

Pituitary failure

Reduction or loss of TSH secretion by the pituitary is a very rare cause of hypothyroidism.

Iatrogenic

Hypothyroidism may occur as an adverse reaction to lithium used in the treatment of mood disorders.

Treatment

Substitution of thyroid hormones by taking thyroxine (T4) tablets. Doses are started with smaller amounts of thyroxine and then slowly titrated under control of TSH levels. Usually the maintenance dose is about 1 to 2 micrograms (µg) per kilogram of body weight.

Controversy exists about the usefulness of administrating triiodothyronine (T3) as well as T4.

Some thyroid deficiency is a side effect of treatment for thyroid cancer, and Graves' disease.

Deficiencies of some dietary minerals can lead to hypothyroidism. Supplementation can be an effective treatment.

Fluoride poisoning has effects very similar to iodine deficiency in 177 conditions [1]. Fluoridated water or other fluoride usage may be counter-indicated.