HYPOTHYROIDISM - The Under-active Thyroid

Hypothyroidism occurs when the thyroid gland produces too little thyroid hormone, and when this happens, the body's functions slow down.

Common Symptoms Include:

• Fatigue and lethargy
• Feeling constantly cold
• Unexplained weight gain
• Depression and lack of concentration
• Slowed heart beat
• Hair loss
• Dry, thickened skin
• Puffy face with eye bags
• Flaking and pitting of the nails

Causes of Hypothyroidism:

• Hashimoto's Disease
This is an autoimmune condition which can lead to hypothyroidism.

• Thyroiditis
Thyroiditis refers to the inflammation of the thyroid gland from whatever cause (eg. Post-partum thyroiditis).  Thyroiditis can lead to hypothyroidism.

• Thyroidectomy (Surgical removal of the thyroid gland)
Sometimes a large portion of the thyroid gland is removed, for instance in the treatment of thyroid cancer or Grave's disease, and the residual thyroid tissue is unable to produce sufficient thyroid hormone for normal body functioning.

• Radioiodine Therapy
Radioactive iodine is given to treat hyperthyroidism.  Hypothyroidism usually results from this form of treatment.

• Certain Medication
Some medication such as lithium (for treatment of psychiatric disorders) and amiodarone (for treatment of abnormal heart rhythms), can sometimes cause hypothyroidism.

• Pituitary Gland or Hypothalamus Malfunction
If “up stream” stimulatory hormones (TRH and TSH) are not produced in sufficient quantities due to abnormal functioning of the pituitary gland or hypothalamus, then the thyroid gland will not produce sufficient thyroid hormone.  There is usually an associated deficiency in other hormones as well, because the hypothalamus and pituitary gland are also involved in the control of many of these hormones.

• Lack of Dietary Iodine
This is a rare cause of hypothyroidism.

• Congenital Hypothyroidism

Diagnosis of Hypothyroidism:

Blood tests showing depressed thyroid hormone levels will confirm the diagnosis of hypothyroidism.  There will also be a correspondingly high level of TSH (see earlier explanation regarding this negative feedback relationship).

Sometimes thyroid hormone levels (T3 and T4) are normal, but TSH levels are raised.  This is a condition known as subclinical hypothyroidism, and it has been found that some of these patients go on to develop clinical hypothyroidism (in which thyroid hormone levels become depressed) with time.

Treatment of Hypothyroidism:

You will be offered thyroid hormone replacement therapy (thyroxine) by your doctor.  In the initial period of starting replacement therapy, you will need to have your blood checked more regularly to see that TSH levels have returned to normal.  Subsequently, you may only require annual checks when your condition becomes more stable.

Over the years, you may find that the dose of thyroid hormone you need goes up.

Find an Endocrinologist