Question

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in the human body, the thyroid gland releases hormones that affect the rate of cellular metabolism. which of the following best describes the negative feedback mechanism that controls how much of this hormone is released?
the cells affected by thyroid hormones are designed to absorb specific amounts of the hormone
when the blood concentration of thyroid hormones reaches a certain level, production stops.
when the cellular metabolism drops below a certain level, thyroid hormone production starts.
the cells that produce thyroid hormones are programmed to die after making a certain amount of hormone

Explanation:

Negative - feedback mechanisms work to maintain homeostasis. In the case of thyroid - hormone regulation, when the blood concentration of thyroid hormones reaches a certain level, it signals the gland to stop production to prevent over - production. This is a classic example of negative feedback. The other options do not describe the negative - feedback mechanism for thyroid - hormone release.

Answer:

When the blood concentration of thyroid hormones reaches a certain level, production stops.