Question

the release of testosterone from the testes is directed by the hypothalamus and pituitary gland. as testosterone concentrations in the blood rise, the hypothalamus and pituitary gland reduce their signaling to the testes to prevent additional testosterone secretion. this is an example of which of the following? antagonistic effect permissive effect negative feedback loop positive feedback loop

Explanation:

• Antagonistic effect: Occurs when two hormones have opposing effects. For example, insulin lowers blood sugar and glucagon raises it. This is not the case here as there is no mention of two hormones with opposing actions.
• Permissive effect: One hormone enables another hormone to act. For instance, estrogen priming the uterus for progesterone's action. This scenario does not fit the permissive effect definition.
• Negative feedback loop: A mechanism where the end - product (in this case, testosterone) inhibits the production or release of the substances (signaling from hypothalamus and pituitary) that led to its production. When testosterone levels rise, it reduces the signaling from hypothalamus and pituitary to the testes, which is a classic negative feedback.
• Positive feedback loop: The end - product enhances the production or release of the substances that led to its production. For example, oxytocin during childbirth where more oxytocin leads to more uterine contractions which in turn lead to more oxytocin release. This is not what is happening with testosterone regulation.

Answer:

Negative feedback loop