1 An adenoma is a part of the gland that has walled itself off from the rest of the gland, forming noncancerous (benign) lumps that may cause an enlargement of the thyroid. Not all adenomas produce excess T-4, and doctors aren't sure what causes some to begin producing too much hormone.  Thyroiditis.
Scratching Itchy Skin Causes Brain To Release Hormone Serotonin, Intensifies Itchy Sensation. While a good scratch may temporarily relieve you of your itch, it actually stimulates serotonin in the brain that intensifies the itchy feeling.
It may start when something rubs, irritates, or scratches the skin, such as clothing. The person begins to rub or scratch the itchy area. Constant scratching causes the skin to thicken. The thickened skin itches, and this leads to more scratching. This then causes more thickening of the skin.