The endocrine glands secrete hormones which are released directly into the bloodstream and are carried throughout the body.
The effect of hormones is much slower than that of neurotransmitters communicating steady, relatively unchanging, messages over prolonged periods of time such as during puberty.
Endocrine glands are ductless as opposed to exocrine glands such as tear ducts.
The major endocrine gland is the pituitary gland, which is only physically part of the brain situated just below the hypothalamus. It produces the largest number of different hormones and controls the secretion of several other endocrine glands.
The pituitary comprises two inependently functioning parts : the anterior and posterior. The former transmits hormones which are thought to be manufactured in the hypothalamus, while the latter is stimulated by the hypothalamus to produce it's own hormones. (extracts taken from (PSYCHOLOGY The Science of Mind and Behaviour - Richard D. Gross, part 2 of the Biological Basis of Behaviour and Experience - 2nd edition).
Here we will concentrate on the effects of the reproductive hormonal system, in particular the female menstrual cycle.
The female cycle and it's variant effects on the brain and subsequent behaviour isn't something to be scoffed at. The pre-menstrual phase can be a cause of moderate to distressful, even suicidal behaviour in certain individuals. Coupled with any neurological condition can lead to extreme distress at certain times of the month.
During informal discussions with females with pre-menstrual difficulties and women with pre-menstrual difficulties coupled with neurological disease, pre-existing minor to major difficulties were accentuated during this phase of the female cycle. For example a minor cluster headache problem may become something so debilitating during this phase, the woman may have to take time off work. If a woman suffers from epilepsy, she may have more intense seizures or more frequent seizures during this phase of her cycle.
The chain of events caused by the complicated workings of the endocrine system can have such a major knock on effect on brain and behaviour, be it through hormonal troubles such as PMS through to diabetes and many other endocrinal conditions, the results can be amazing to disastrous.