Positive feedback describes an event in which a pathway generates a response that further triggers the pathway, increasing the pathway effects. In contrast, negative feedback occurs when a pathway generates a response to inhibit the pathway origin, diminishing the pathway effects. Negative feedback is a common control mechanisms in the body to maintain homeostasis, while positive feedback is inherently designed to disrupt homeostasis.

Fever during illness is enhanced via a positive feedback system that only ends once the illness begins to alleviate. Similarly, contractions during labor will intensify via positive feedback oxytocin stimulation until the child is born. Osteoporosis is caused by an imbalance in the negative feedback system that controls blood calcium. This imbalance simply means that bone is lost more than it is gained, and is still an example of negative feedback.

Triiodothyronine (T3) employs a negative feedback mechanism, meaning that when blood serum concentrations of T3 become too high, receptors on the thyroid gland inhibit the release of additional T3.

In contrast, a positive feedback mechanism would encourage additional release of a hormone when levels are high, resulting in an exponential increase in the hormone effects. An example of a positive feedback mechanism is the release of oxytocin during childbirth to help the uterus contract.

Oxytocin employs a positive feedback mechanism, meaning that existing levels of oxytocin encourage additional release of oxytocin. This results in an exponential increase in the hormone's effects.

In contrast, a negative feedback mechanism would prevent additional release of a hormone when levels of the existing hormone were too elevated. This results in stable homeostasis around a constant hormone concentration in the blood.

Thyroid-stimulating hormone (TSH) levels would be decreased.

The thyroid hormones T3 and T4 act in a negative feedback loop to regulate thyroid activity. Release of TSH increases thyroid activity, while release of the thyroid hormones decreases thyroid activity by suppressing further release of TSH. Since the thyroid is overstimulated in Grave's Disease, excess T3 and T4 are being produced. These hormones will act on the feedback loop to suppress TSH release, lowering TSH levels in individuals with this disease. Since the antibodies bind to the TSH receptors, there are increased levels of T3 and T4 in the body, which negatively inhibit the production of TSH because the body is already flooded with the products of TSH action.

Injecting insulin into the body delivers it directly into the bloodstream, while consuming an insulin pill would require it to pass through the gastrointestinal tract. In the gut, the pill would be degraded first and then absorbed into the bloodstream. This entire process would result in a small amount of insulin circulating in the blood, and therefore be much less effective than an insulin injection. Additionally, injecting insulin directly allows more rapid administration of a more consistent dose. 

Androgens and estrogens, the sex hormones, feedback to inhibit somatotropins, the growth hormones. In humans, the sex hormones are produced in puberty, disabling the growth plates and halting growth.