Humans and gastrointestinal parasites might have co-evolved in such a way that the parasites actually help regulate to human immune system to prevent against allergies, according to a study conducted by researchers from the University of Nottingham.
How it All Works (references)
The thyroid gland is the biggest gland in the neck. It is situated in the anterior (front) neck below the skin and muscle layers. The thyroid gland takes the shape of a butterfly with the two wings being represented by the left and right thyroid lobes which wrap around the trachea. The sole function of the thyroid is to make thyroid hormone. This hormone has an effect on nearly all tissues of the body where it increases cellular activity. The function of the thyroid therefore is to regulate the body's metabolism.
How Your Thyroid Works
"A delicate Feedback Mechanism"
thyroid gland is a small gland, normally weighing less than one ounce, located
in the front of the neck. It is made up of two halves, called lobes, that lie
along the windpipe (trachea) and are joined together by a narrow band of thyroid
tissue, known as the isthmus.