Question

1: Briefly describe how the thyroid and parathyroid hormones are controlled.            

2: Thyroid hormones increase metabolism. Why is giving thyroid hormones not recommended to treat obesity?

Answer 1

Ans) 1) When the calcium level is high in the bloodstream, the thyroid gland releases calcitonin. Calcitonin slows down the activity of the osteoclasts found in bone. This decreases blood calcium levels. When calcium levels decrease, this stimulates the parathyroid gland to release parathyroid hormone.

Thyroid-releasing hormone (TRH) from the hypothalamus stimulates TSH from the pituitary, which stimulates thyroid hormone release. As blood concentrations of thyroid hormones increase, they inhibit both TSH and TRH, leading to "shutdown" of thyroid epithelial cells.

2) Thyroid hormones stimulate diverse metabolic activities most tissues, leading to an increase in basal metabolic rate. One consequence of this activity is to increase body heat production, which seems to result, at least in part, from increased oxygen consumption and rates of ATP hydrolysis.

- An unexplained change in weight is one of the most common signs of a thyroid disorder. Weight gain may signal low levels of thyroid hormones, a condition called hypothyroidism. In contrast, if the thyroid produces more hormones than the body needs, you may lose weight unexpectedly.