Clinical meaning
The endocrine system maintains homeostasis through hormonal signaling pathways that operate via negative feedback mechanisms between the hypothalamus, anterior pituitary, and target endocrine glands. Thyroid hormone synthesis requires iodine uptake by the sodium-iodide symporter, thyroglobulin iodination by thyroid peroxidase, and coupling of monoiodotyrosine (MIT) and diiodotyrosine (DIT) to form T3 and T4. Insulin, produced by pancreatic beta cells in the islets of Langerhans, facilitates glucose uptake through GLUT4 transporter translocation to cell membranes in muscle and adipose tissue. Cortisol, the primary glucocorticoid produced by the adrenal cortex under ACTH stimulation, regulates glucose metabolism, immune function, and the stress response through intracellular glucocorticoid receptors.
Exam relevance
Risk factors: - Type 1 DM: HLA-DR3/DR4 genetic susceptibility - Type 2 DM: Obesity, sedentary lifestyle, family history - Graves disease: Female sex, autoimmune history - Hashimoto thyroiditis: Female sex, family history - Adrenal insufficiency: Chronic corticosteroid use - Pheochromocytoma: MEN2 syndrome, family history