As an endocrinologist I treat patients with thyroid disorders. The thyroid is a small butterfly-shaped gland just above your collarbone in front of the neck. It makes thyroid hormone, a substance that controls your metabolism.

An enlargement of the entire thyroid or any part of the thyroid such as a fluid-filled cyst or a solid nodule is called a goiter. Thyroid function is frequently normal in patients with goiter, with no other symptoms except a bulge in the neck.

But a goiter may be associated with an increase in thyroid hormone which is called hyperthyroidism, where your metabolism can be very fast and this is associated with weight loss, palpitations, sweats, tremors of the hands, feeling warm and characteristic eye changes (stare).

If the goiter causes hypothyroidism, this is the opposite of the previous condition. Having less thyroid hormone, metabolism is slower, leading to weight gain, slow heart rate, constipation and feeling cold.

There are many misbeliefs about goiter. It is not caused by shouting, singing, drinking cold water, lifting heavy things, straining with activity or childbirth, or from eating certain foods. You can do all these things without causing your thyroid to become enlarged.

The most common cause of goiters worldwide is a lack of iodine in the diet, which is needed to make thyroid hormone. Other causes are autoimmune disorders where antibodies produced by your immune system mistakenly attack your thyroid gland as in Hashimoto's thyroiditis or when the immune system causes an overproduction of thyroid hormone as in Graves' disease.