Endocrine PathologyEndocrine System:Highly interactive system of glands that are distributed throughout the body witha variety of physiologic roles. They carry out these tasks using special chemical messengers called hormones. Endocrine glands are ductus glands, which are, distributed widely – pituitary gland, hypothalamus, pancreas, thyroid, adrenals, etc.Hormones can be secreted in one of three basic patterns:oDiurnal (or circadian pattern)– occurs every 24 hours. Influenced by internal clock, sleep wake cycles, food intakeEx of hormone secreted in circadian pattern is cortisol (a glucocorticoid steroid hormone produced in the adrenal glands, considered a stress hormone. One of it’s primary roles is increasing gluconeogenesis which is stimulating the production of glucose. Peaks in the morning and drops at night and this cycle repeats as the day progressesoPulsatile or cyclic natureEx. Insulin (basal insulin levels oscillate and the amplitude of theseoscillations increases after meals. But the periodicity remains constant and it’s driven by calcium concentration within the beta cells. It is stimulated by pacemaker neurons in the pancreas similar to the way that we have pacemaker cells in the cardiac myocytes and pacemaker cells involved in the peristalsis. In this case these pacemaker cells help to give you this oscillating secretion of insulin throughout the day, which then can increase depending on glucose load. oAltered or changing levels of some sort of substrateEx. Release of calcitonin. As levels of calcium increase, there is an increase in the production and release of calcitonin in the thyroid. Hormone release can also be regulated by one of two feedback mechanismsoNegative feedbackThe release of a hormone will directly inhibit the release of another hormone. Ex. Release of thyroid hormone. This starts with the release of thyrotropin releasing hormone from the hypothalamus which then stimulates the release of thyroid stimulating hormone from the anterior pituitary, which then stimulates the thyroid to releaseboth T3 and T4 which are active thyroid hormones. That T3 and T4then binds to specific receptors in the hypothalamus, which when the levels are appropriate will shut off the release of thyrotopin releasing hormone. oPositive feedback
The release of a hormone stimulates an increased release of that same hormone and it keeps increasing in a crescendo type fashionEx. Ferguson reflex during labor: stimulation of the uterus results in increased release of oxytocin and as that oxytocin interacts and creates stronger and stronger reactions, there’s more and more oxytocin released. When hormones are released from a particular gland, they are then free to travelabout in search of their intended organ. With regards to peptide hormones, these are mostly water-soluble so they travel both free and unbound.