ABSTRACT
The hormones secreted by the endocrine glands include adrenaline, noradrenaline, glucagon, and insulin, and they mediate their effects by activating inactive enzymes present within the cell. There are essentially three classes of hormones, these being amine hormones, peptide hormones and steroid hormones. The amine hormones include the catecholamines adrenaline and noradrenaline, the peptide hormones include glucagon and insulin, whereas the steroid hormones include the sex hormones estrogen and testosterone. The key hormones concerned with regulating energy metabolism are the amine and peptide hormones, although the steroid hormones cortisol and growth hormone also affect metabolic processes. These hormones have as their target tissues either muscle, adipose tissue or liver, and regulate the processes glycogenolysis, glycolysis, lipolysis, gluconeogenesis, and glycogenesis, as well as protein degradation and synthesis. The metabolic processes involved in energy production and storage are regulated by hormones.
