ABSTRACT
A hormone is a chemical substance released from a ductless gland (or group of secretory cells) directly into the bloodstream in response to a stimulus and exerts a specific regulatory effect on its target organ(s) via receptors (4). The main endocrine organs of the body are as follows:
Endocrine dysfunction can occur at different levels, for example, at the level of hormone production and secretion (e.g. failure to produce a hormone), or at the level of the target organ (e.g. failure to respond to a hormone due to lack of receptors). It can be classified into hyper-and hyposecretion. Hypersecretion can be due to a tumour that secretes excess hormone (e.g. pituitary adenoma) or due to an inappropriate stimulation (e.g. in Graves’ disease antibodies stimulate the thyroid to produce excess T4). Hyposecretion can be due to the inability of cells to produce hormone (e.g. in hypothyroidism there is a reduction in the amount of T4 secreted) or due to hypofunction of a gland (e.g. excess somatostatin release from the hypothalamus results in a decrease in the amount of growth hormone released by the anterior pituitary).
