Diseases of the endocrine system usually are based on an abnormal reduction of a
ID: 3506162 • Letter: D
Question
Diseases of the endocrine system usually are based on an abnormal reduction of a hormone's availability, called hyposecretion or an abnormal increase, called hypersecretion. In the condition "hypothyroidism," the thyroid hormones are below-normal levels, perhaps because of inherited deficiency involving the thyroid physiology, or deficiency in dietary iodine (iodine is necessary for the manufacture of thyroid hormones), or a tumor of the pituitary gland. Advanced stages of hypothyroidism result in the growth (hypertrophy) of the thyroid gland producing large goiters. Using a negative feedback loop, explain how iodine deficiency results in goiters. 1.Explanation / Answer
Answer
Thyoid gland releases thyroid hormones that regulates metabolic processes in the body.
Normally, Thyroid releasing hormone(TRH) secreted by hypothalamus stimulates the release of thyoid stimulating hormone (TSH). TSH in turn triggers the release of thyroid hormones from thyroid gland.
When there is enough thyoid hormone concentration in blood, a negative feedback mechanism is activated. As there is increase in thyroid hormone levels in blood, a negative signal is sent to hypothalamus that inhibits the release of TRH. This eventually stops the secretion of TSH and thyroid hormones.
Thyroid hormones are triiodothyronine (T3) and tetraiodothyronin (T4) / thyroxine. Both of them have iodine as their main component. Iodine is very important micronutrient for synthesis of these thyroid hormone.
If there is relatively less dietary intake of iodine and significant low iodine levels in blood, thyoid hormones will not be synthesized. Due to lack to thyroid hormones, negative feedback loop cannot be activated. This results in increased secretions TRH and TSH hormones. Constant stimulation of thyroid gland by TSH leads to hyperthrophy of cells and enlarged thyroid gland.
This condition is known as goiter.
This is the mechanism for low iodine levels resulting into goiter.