Parathyroid Gland Endocrinology Lecture PDF

PARATHYROID GLAND Parathyroid Glands: Four glands behind the thyroid. Parathyroid Hormone (PTH): Regulates calcium and phosphate levels.  Origin: Parathyroid glands arise from pharyngeal pouches. Development: Superior glands: from 4th pouch Loading… Inferior glands:...

PARATHYROID GLAND Parathyroid Glands: Four glands behind the thyroid. Parathyroid Hormone (PTH): Regulates calcium and phosphate levels.  Origin: Parathyroid glands arise from pharyngeal pouches. Development: Superior glands: from 4th pouch Loading… Inferior glands: from 3rd pouch Migration: Move into the neck, leading to variable positions. Size & Color: Small, pea-sized, yellow-brown glands (30-50 mg each). Position: Superior glands have a consistent location; inferior glands vary. Blood Supply: Branches of the inferior thyroid arteries. Anatomical Variation: ~5% lack one or more glands; no clinical effect if at least one remains functional. Loading…  Cell Types: Chief cells and oxyphil cells. Chief Cells: Produce and store parathyroid hormone. Oxyphil Cells: Rich in mitochondria; role unclear.  Parathyroid Hormone (PTH): Main regulator of calcium and phosphate balance. Vitamin D: Supports PTH by increasing calcium absorption; requires PTH for activation. Calcium (Ca²⁺): Essential for: Bone formation Muscle contraction Enzyme cofactor Membrane stability in muscles and neurons Blood coagulation Mode of Action of Calcium (Ca²⁺) Calcium as a second messenger: Binds to proteins, altering their structure and function. 1. Stimulation of G-protein−coupled receptors opens transmembrane Ca²⁺ channels. 2. Ca²⁺ influx increases intracellular Ca²⁺ concentration. 3. Intracellular Ca²⁺ activates extracellular signal−regulated kinases. 4. Kinase activation changes biological activity, affecting cytoplasm and nucleus, influencing gene transcription. Distribution of Calcium in the Body Total calcium: 1−2 kg in adults 99% in teeth and bones (as hydroxyapatite crystals) 1% intracellular Loading…