Thyroid hormone

Question 1

Describe the structure of the thyroid gland

Answer 1

Parafollicular cells- secrete a peptide hormone called calcitonin which can cause medullary carcinomas
Thyrocytes are organised into special follicles.

Question 2

describe the biosynthesis of thyroid hormone

Answer 2

Diagram in slides

Question 3

What are the 2 primary categories of physiological effects of thyroid hormones?

Answer 3

Effects on cellular differentiation and development, on the nervous system in particular
Effects on metabolic pathways and use of carbohydrates, lipids and proteins

Question 4

Name some of the physiological effects of thyroid hormone.

Answer 4

T3 and T4 promote accelerated metabolism.
TH’s promote growth of neurons and stimulate maturation of the CNS
Increases responsiveness to catecholamines by increasing number of receptors.

Question 5

How is TH regulated?

Answer 5

Negative feedback loop

Question 6

What causes hyperthyroidism

Answer 6

Autoimmune disease-graves disease
Autoantibodies stimulate thyrotrophin receptors on thyroid gland follicle cells leading to continual stimulation of thyroid hormone secretion.
Benign tumour of thyroid cells causing enlargement of the gland and increased hormone secretion.

Question 7

What causes hypothyroidism

Answer 7

Inflammatory/autoimmune disease (Hashimoto disease)
Antibodies attack specific thyroid cellular components, causing gland damage
Defective hypothalamic and pituitary function causing insufficient thyrotropin secretion for normal stimulation of thyroid glands

Question 8

What is goitre?

Answer 8

Enlarged thyroid gland
When dietary intake of iodine is too low for normal TH production, TSH secretion increases and thyroid cells proliferate to try to make up for the lack of T3 and T4.