Question 3(p.2)

College Answer

This question sought an understanding of the physiological effects of thyroid hormones. The
major area of weakness for candidates was a lack of detailed understanding of the
physiological actions of thyroid hormones and/or providing an answer that predominately
listed clinical manifestations. A good answer would have included the following points -
Stimulation of Carbohydrate Metabolism - all aspects of carbohydrate metabolism,
including rapid uptake of glucose by the cells, enhanced glycolysis, enhanced
gluconeogenesis, increased rate of absorption from the gastrointestinal tract, and increased
insulin secretion
Stimulation of Fat Metabolism - all aspects of fat metabolism are also enhanced
lipids are released from fat stores and increased oxidation of free fatty acids by the cells -
decreases the concentrations of cholesterol, phospholipids, and triglycerides in the plasma,
even though it increases the free fatty acids

• Increased Basal Metabolic Rate – increased CMRO2
• Increased Requirement for Vitamins
• Increased vasodilatation, Cardiac Output, heart rate (not BP), contractility
• Increased Respiration – secondary to increased metabolism
• Increased Gastrointestinal Motility and secretions
• Excitatory Effects on the Central Nervous System, seizures and insomnia
• Effect on the Function of the Muscles – stimulates contractility and metabolism, buttoo much leads to the muscles become weakened because of excess protein catabolism. Alsomuscle tremor by increased reactivity of the neuronal synapses in the areas of the spinal cord that control muscle tone.

Effect on Other Endocrine Glands - . increases the rate of glucose metabolism
everywhere in the body and therefore causes a corresponding need for increased insulin and
glucagon secretion by the pancreas.
Also, increase bone formation and, as a consequence, increases the need for
parathyroid hormone. Thyroid hormone also increases adrenal glucocorticoid metabolism by
the liver.