Group 1 hormone: Hormones have intracellular receptors and affect gene expression.

1. Hormones in this group are lipophilic and derived from cholesterol and amino acid derivative T3 and T4.

2. After secretion from specific glands, these hormones associate with transport proteins.

3. As soon as they bind to the plasma membrane of target cells, they detached from binding protein (carrier protein).

4. The free hormone readily traverses the plasma membrane of target cells, and encounter receptors in either the cytosol or nucleus of the target cells.

5. The ligand receptor complex assumed to be intracellular messenger in this group.
The general feature of these hormones are:
a) The hormone diffuses through the plasma membrane of all cells but only encounter their specific, high affinity receptor in target cells.

b) The hormone receptor complex undergoes a temperature and self dependent activation reaction that results in size, conformation, and surface charge changes that render it able to bind to (DNA) chromatin.

c) The hormone receptor complex binds to a specific region of DNA called the hormone response element (HRE) and activates or inactivates specific genes.

d) By selectively affecting gene expression and the production of the respective messenger RNAs, the amount of specific proteins are changed and metabolic processes are influenced.