Define the Gene Activation - Mechanism of Hormone Action
A second important way by which the hormone affects cell function is gene activation. This is the mechanism of hormonal control utilized by steroid hormones. In this case, the activating hormone reacts with a receptor substance in the cell cytoplasm and the combination of the hormone and the receptor then migrates into the nucleus where it activates one or more specific genes.
These then promote specific functional effects within the cell. Thus, protein hormones (except thyroid hormones) act via cyclic AMP and steroid hormones including thyroid hormones act through cytoplasmic receptors before they migrate to nucleus. Through these two types of mode of action, the hormones can regulate growth, nutrition and metabolic activity of the cell. Hence, cellular nutrition and function are dependent on the hormonal action.