Endocrine System Foundations

Endocrine glands release hormones into the bloodstream. Those hormones travel to target tissues and alter processes such as glucose use, metabolic rate, fluid balance, calcium concentration, stress response, growth, and reproduction. The hypothalamus and pituitary coordinate several glands, while feedback loops prevent hormone levels from drifting too far from the physiologic range. This feedback design explains why endocrine disorders often produce findings in several body systems at once. Too little thyroid hormone slows metabolism, so the patient may become fatigued, cold-intolerant, constipated, bradycardic, and cognitively slowed. Too much thyroid hormone increases metabolic demand, producing heat intolerance, tremor, tachycardia, weight loss, anxiety, and frequent stools. The symptoms are not random; they are the downstream effects of altered cellular activity. Insulin lowers blood glucose by helping glucose move from the bloodstream into cells and by suppressing glucose production by the liver. Insulin deficiency or resistance leaves glucose in the circulation. The resulting hyperglycaemia draws water into the urine, causing polyuria, thirst, dehydration, and eventually electrolyte disturbance. If insulin deficiency becomes severe, fat is broken down and ketones accumulate, creating diabetic ketoacidosis (DKA)....