Hormone Activity: Half-Life, Onset, Duration, and Interaction (Nursing)

00:00 So let's take a closer look at the hormonal activity itself. Hormones are going to circulate in our blood either free or bound. Steroid hormones and thyroid hormones are usually attached to plasma proteins while other hormones are going to circulate without being attached to anything or without carriers. The concentration of circulating hormones usually reflects its rate of release as well as the speed of which the hormone is inactivated or removed from the body. So how are hormones removed from the body? Hormones can be removed from the blood by degrading enzymes, by the kidneys, or by the liver. We measure how long a hormone remains or is removed from the body by a measurement known as the half-life. Half-life is the time required for the level of the hormone in blood to decrease by half. This is going to vary anywhere from a fraction of a minute to almost a week depending on the hormone that we're talking about. Another measurement of hormonal activity is a value known as onset. Onset refers to the amount of time it takes for target cell to react to a hormone. Hormones have different response times. Some response times are going to be immediate whereas some especially with steroids can take hours to days for a response to occur, and some will be inactive until they enter the target cell. Finally, we have duration. Duration is a response that is usually very limited. The duration of the response measures how long the hormonal response actually lasts. This can range anywhere from 10 seconds to several hours and the effects may disappear rapidly as the blood levels of the hormone drop but sometimes the effects may persist even after the hormone blood levels are starting to dissipate. Multiple hormones may act on the same target at the same time. This is referred to as permissiveness where one hormone actually cannot exert its effects without the presence of another hormone. An example of this is the reproductive hormones that need thyroid hormone in order to actually have an effect on their target cells. Another way multiple hormones act on the same target cell is something called synergism. In synergism, more than 1 hormone will produce the same effects on the target cell. This causes an amplification of that effect. An example of this is glucagon and epinephrine which both are going to act on the liver to release glucose.

03:28 A 3rd type of interaction between hormones is antagonism. Antagonism means that one or more hormones are going to oppose the action of another hormone. A good example of this is insulin which is going to decrease blood glucose levels and glucagon which increases blood glucose levels.