Final answer:
Hormone release and timing are regulated by feedback mechanisms, predominantly through negative feedback loops, which maintain homeostasis by keeping hormone levels within a narrow range. Positive feedback loops exist but are less common and tend to amplify the response, as observed with oxytocin during labor.
Step-by-step explanation:
The statement (A) 'Amount and timing of hormones released are regulated by feedback mechanisms' is true. Hormones are indeed regulated via feedback mechanisms which include both negative and positive feedback loops. The negative feedback loop is the most common form of regulation in hormone production and release. An example is the regulation of thyroid hormones, where increased levels of hormones provide a feedback to the hypothalamus and pituitary to inhibit further release. Conversely, positive feedback amplifies the response; a classic example is the role of oxytocin during labor, where more hormone is released as a response to uterine contractions.
It is also true that vasopressin is synthesized by the hypothalamus, and prolactin, like most hormones, is regulated by a negative feedback loop. Additionally, melatonin is secreted by the pineal gland, growth hormone by the anterior pituitary gland, thyroid-stimulating hormone also by the anterior pituitary gland, and aldosterone by the adrenal cortex.
Overall, hormone regulation is crucial for maintaining homeostasis within the body, and disruptions can lead to various medical conditions, such as diabetes mellitus due to insufficient insulin production. The regulation by negative feedback maintains hormone concentration within a narrow range, ensuring the body's normal function.