Anaesthesia Fundamentals | Physiology | Thyroid and Parathyroid Hormones and Calcium Homeostasis

Thyroid and Parathyroid Hormones and Calcium Homeostasis
Session Overview
Description
This session is split into two sections. The first outlines the physiology of the thyroid gland and homeostatic control of thyroid hormone secretion. The second describes and explains the body’s mechanisms for controlling plasma calcium concentration.

Learning Objectives
By the end of this session you will be able to:

• Describe the regulation, synthesis and release of thyroid hormones
• Describe the target sites and mode of action of thyroid hormones
• Interpret basic thyroid function tests
• Describe the regulation of plasma calcium concentration
• Describe the hormones involved in the regulation of calcium concentration, and their secretion

Thyroid hormones act throughout the body to control growth and metabolism via intracellular receptors. Synthesis and release of these hormones are controlled through classic feedback mechanisms by hypothalamic and anterior pituitary hormones.

Perioperative morbidity is significantly increased in patients undergoing surgery who are either hyperthyroid or hypothyroid, so it is important to be able to identify these patients both clinically and biochemically.

Calcium homeostasis is achieved by the influence of three hormones:

• Parathyroid hormone (PTH)
• 1,25-dihydroxycholecalciferol
• Calcitonin

This system acts autonomously, but clinically it is important to identify patients whose plasma free calcium levels are abnormal.