30 Questions
What enzyme promotes the oxidation of iodine in the formation of iodine capable of combining with tyrosine?
Thyroid peroxidase
What is the process of binding iodine with the thyroglobulin molecule called?
Organification
Which molecule contains up to 30 thyroxine molecules and a few triiodothyronine molecules?
Thyroglobulin
What is the first step in the iodization of tyrosine during the process of iodination and coupling?
Monoiodotyrosine
What molecule is responsible for the 'organification' of the thyroglobulin with iodine?
Iodinase
What substance accompanies thyroid peroxidase in promoting the oxidation of iodide ions to iodine?
Hydrogen peroxide
Which hormones are commonly known as T4 and T3?
Triiodothyronine and thyroxine
What happens to the basal metabolic rate (BMR) when there is a complete lack of thyroid secretion?
It decreases to 40-50% below normal
Which hormone controls thyroid secretion primarily?
Thyroid-stimulating hormone (TSH)
What percentage of metabolically active hormones secreted by the thyroid gland is thyroxine?
93%
What is the primary function of triiodothyronine (T3) and thyroxine (T4)?
Increase the BMR
Which hormone is also secreted by the thyroid gland apart from T3 and T4?
Calcitonin
What is the main effect of thyroid hormones on gene transcription?
Activate transcription of large numbers of genes
How does thyroid hormone affect glucose metabolism?
Stimulates rapid uptake of glucose by the cells
Which of the following statements about fat metabolism under thyroid hormone influence is correct?
Fat metabolism is enhanced
What is the result of the overall increase in cellular metabolic enzymes caused by thyroid hormone?
Enhanced synthesis of structural proteins
Why are thyroid hormones released slowly to tissue cells?
Because of high affinity of plasma-binding proteins for thyroid hormones
How does the effect of thyroid hormone on carbohydrate metabolism impact insulin secretion?
Increases insulin secretion
What effect does increased thyroid hormone have on the concentrations of cholesterol, phospholipids, and triglycerides in the plasma?
Decreases cholesterol, phospholipids, and triglycerides
What is the primary role of lipids when they are mobilized rapidly from fat tissue?
Accelerate the oxidation of free fatty acids by cells
How does hyperthyroidism typically affect the size of the thyroid gland in patients?
Increases the size significantly
Which protein has the highest binding strength for thyroxine transport in the blood?
Throxine-binding globulin (TBG)
What effect does increased thyroid hormone have on the size of the thyroid gland?
Triples the size
What physiological consequence results from the rapid mobilization of lipids from fat tissue?
Accelerates the oxidation of free fatty acids by cells
What is the underlying cause of hyperthyroidism in Graves' disease?
Antibodies binding to thyroid cell receptors
What do thyroid-stimulating immunoglobulins (TSIs) do in individuals with Graves' disease?
Promote thyroid growth and hormone production
How does Graves' disease affect the size of the thyroid gland?
It enlarges the thyroid gland
What is a common symptom associated with a goiter?
Swollen neck
What do radioactive iodine uptake studies indicate in hyperplastic glands?
Excess thyroid hormone secretion
In Graves' disease, what role do TSIs play in the production of thyroid hormones?
Stimulate excess hormone production
Test your knowledge on thyroid hormones and their functions with this quiz. Learn about the role of thyroxine and triiodothyronine in regulating the body's metabolic rate.
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