Overactive Thyroid Gland
The overactive thyroid means increase function of the thyroid gland and the production of thyroid hormones. The situation has usually wide negative effects on the patient’s organism and some its forms may be even lethal.
To understand the issue, it is good know some information about the activity of the thyroid gland. This organ is located in the neck in front of the trachea and consists of two lobes connected in the middle by a narrow neck. Thyroid cells are capable of capturing iodine from the blood and use it to produce thyroid hormones known as thyroxine (T4) and triiodothyronine (T3). These hormones have a broad spectrum of effects on the metabolism of nutrients and energy. The thyroid gland includes four parathyroid glands (two in each lobe), whose function affects the calcium and bone metabolism.
The majority of organs producing hormones are functionally connected with the brain and the thyroid gland is no exception. The production of thyroid hormones is controlled by two brain centers known as hypothalamus and pituitary gland.
The hypothalamus produces substance known as TRH acting on the pituitary gland, the pituitary gland releases additional substance (TSH) acting directly on the thyroid and causing increased production of T4 and T3 hormones. Quite logically, elevated serum concentration of T4 and T3 reduce the amount of produced TRH and TSH to adjust a feedback.
In fetuses and neonates, the hormones affect proper development of the brain. In adult humans, they are important for body metabolism, production of energy, maintenance of cholesterol levels, heart rate and both the physical and mental activity.
There are multiple possible cause of overactive thyroid gland. There is an autoimmune disease, which damages and irritates the thyroid cells to increased production of the hormones. When there is present contemporary bulging of the eyes, we name the condition as the Graves-Basedow disease. The eye protrusion is caused by autoimmune damage of the tissue behind the eye and local accumulation of connective tissue.
The other causes of overactive thyroid are thyroid tumors. However, the tumors with cells producing the excessive amount of hormones tend to be benign.
Benign tumors of the brain growing from the hypothalamus and pituitary gland may increase the production of TRH and TSH and by this mechanism; they may increase the stimulation of the thyroid gland.
The symptoms of excessive production of the thyroid hormones are logically to some extent opposite to the symptoms of underactive thyroid. The person with overactive thyroid suffers from unwanted weight loss (but with increased appetite), shaking hands, excessive sweating, diarrhea, heat intolerance, brittle hair, excessive mental activity, nervousness, aggressiveness and general irritability. The heart rate is increased and palpitations occur. In addition, there is higher risk of arrhythmias, especially of the atrial fibrillation.
The most serious complications are cardiovascular and sudden bouts of hyperthyroidism may cause severe arrhythmias or acute heart failure.
Increased production of thyroid hormones can be solved by special medications that suppress their production (thyrostatic drugs. The se drugs may be combined with medications decreasing the heart rate such as the beta-blockers. Sometimes, the surgical removal of the thyroid gland is performed and the subsequently missing hormones are regularly administered in tablet forms. If we do not want to perform the surgical operation, the situation may be solved by administering a dose of radioactive iodine. This iodine is just as normal iodine is taken up by thyroid cells that are then disposed of radioactivity.