Endocrine System — Key English Terminology

1.The hypothalamus secretes releasing or inhibiting hormones to control the anterior pituitary.

2.Anterior pituitary hormones include: Growth hormone GH for growth and metabolism; Thyroid-stimulating hormone TSH stimulates the thyroid; Adrenocorticotropic hormone ACTH stimulates the adrenal cortex; Luteinizing hormone LH triggers ovulation and testosterone secretion; Follicle-stimulating hormone FSH matures sperm and oocytes; Prolactin PRL drives milk secretion.

3.Posterior pituitary hormones: Antidiuretic hormone ADH, also called vasopressin, drives water reabsorption in the collecting duct. Oxytocin causes uterine contraction and lactation.

4.Thyroid gland: Thyroxine T4 and triiodothyronine T3 set the metabolic rate and oxygen consumption. Calcitonin lowers blood calcium via osteoblast bone formation.

5.Parathyroid hormone, PTH, raises blood calcium via osteoclast bone resorption — opposite of calcitonin.

6.Adrenal cortex: Cortisol handles stress response, raises blood glucose, and is anti-inflammatory. Aldosterone increases sodium reabsorption, raising blood pressure.

7.Adrenal medulla: Epinephrine, also called adrenaline, drives the fight or flight response.

8.Insulin is secreted by pancreatic beta cells in response to high blood glucose. It lowers blood glucose by promoting glucose uptake into cells via GLUT4. Mechanism: receptor tyrosine kinase, then GLUT4 translocation to the membrane.

9.Glucagon is secreted by pancreatic alpha cells in response to low blood glucose. It raises blood glucose by promoting glycogen breakdown — glycogenolysis. Mechanism: GPCR, then cyclic AMP, then PKA.

10.Mnemonic: Insulin lets glucose IN — lowers glucose. Glucagon equals glucose GONE — raises glucose.

11.Pineal gland secretes melatonin for the sleep-wake cycle. Thymus secretes thymosin for T cell maturation.

12.Negative feedback example: high T3 or T4 inhibits TRH and TSH secretion. This is the dominant feedback type in endocrine homeostasis.