What effect does TSH have on the thyroid gland?

The correct choice is that TSH, or Thyroid Stimulating Hormone, increases the release of thyroxine from the thyroid gland. TSH is secreted by the anterior pituitary gland, and its primary role is to stimulate the thyroid gland to produce and secrete the hormones thyroxine (T4) and triiodothyronine (T3). These hormones are crucial for regulating metabolism, growth, and development in the body.

When TSH binds to its receptors on the thyroid cells, it prompts the synthesis and release of thyroxine, which then helps to increase metabolic activity throughout the body. This process is part of a feedback mechanism involving the hypothalamus and pituitary gland, where low levels of thyroxine signal the release of more TSH, thereby maintaining a balanced level of thyroid hormones in circulation.

The other options do not accurately reflect the action of TSH on the thyroid gland.