Lecture 26: Thyroid Diseases

Question 1

Recall the thyroid and parathyroid glands.

Answer 1

Question 2

Describe the structure and function of thyroid cells.

Answer 2

Question 3

Follicles are enveloped by ________________ which synthesise and secrete _________ into the viscous colloid. __________________ lie between follicles and secrete __________________.

Answer 3

Follicles are enveloped by cuboidal epithelial follicular cells which synthesise and secrete T hormones into the viscous colloid. Parafollicular cells (C-cells) lie between follicles and secrete Calcitonin

Question 4

Describe calcitonin and thyroglobulin.

Answer 4

Calcitonin is stimulated by increases in serum calcium concentration and protects against the development of hypercalcemia

Thyroglobulin [Tg] produced by follicular cells bound to thyroid hormone

Question 5

Recall the hypothalamic-pituitary-thyroid axis and the mechanism of action of thyroid hormones.

Answer 5

Question 6

Recall the mechanism of action of steroid hormones.

Answer 6

Question 7

Recall the biosynthesis of T3 and T4.

Answer 7

Question 8

Most regulation of thyroid hormone occurs in the __________ via __________________________.

Answer 8

Question 9

Main metabolism of thyroid hormone is via ________________

Answer 9

Question 10

Recall thyroid hormone function.

Answer 10

Question 11

Recall two broad categories of thyroid diseases.

Answer 11

• Diffuse Non-toxic (Simple) Goiter – asymptomatic enlargement of thyroid
• Overactive thyroid gland
  
  • Hyperthyroidism - increase in level of hormone → toxic effects
    
    • Diffuse hyperplasia of the thyroid – most common (e.g. Graves disease)
    • Hyperfunctional multinodular goiter
    • Hyperfunctional thyroid adenoma
• Underactive thyroid gland
  
  • Hypothyroidism - decrease in level of hormone → impaired development in infants and slowing of physical and mental ability in adults
    
    • Congenital
    • Autoimmune
    • Iatrogenic – surgery, radiation, drugs

Question 12

Hyperthyroidism leads to an increase in ________________ and overactivity of the ____________________. Mention the effects of these two changes.

Answer 12

Question 13

Describe simple goiter.

Answer 13

Question 14

Describe the aetiology of Grave’s Disease.

Answer 14

Question 15

Describe briefly about Grave’s Disease.

Answer 15

• Most common cause of hyperthyroidism in iodine-replete populations
• Wide, staring gaze, exophthalmos - sympathetic overstimulation of eye muscles muscles & connective tissue build-up behind the eye
• ↑ levels of free T4 & T3 and ↓ levels of TSH in blood
• Diffuse hypertrophy and hyperplasia of follicles and lymphoid infiltrates

Question 16

Describe multinodular goiter.

Answer 16

Question 17

Recall diagnosis and treatment of hyperthyroidism.

Answer 17

Question 18

Recall the types of thyroid neoplasms.

Answer 18

• Based on location
  
  • Primary Tumour: epithelial, malignant lymphomas, mesenchymal tumours
  • Metastatic Tumours
• Based on cell type
  
  • Tumours of follicular cells
    
    • Benign (adenomas): follicular adenoma
    • Malignant (carcinomas)
      
      • Follicular adenoma (10-20%)
      • Papillary carcinoma (75-85%)
  • C-cell Tumours: medullary thyroid carcinoma

Question 19

Recall possible pathways leading to thyroid neoplasms

Answer 19

Question 20

Recall evolution of thyroid neoplasms.

Answer 20

Question 21

Describe papillary carcinoma.

Answer 21

Question 22

Describe MTC.

Answer 22

Question 23

Recall features of hyperthyroidism

Answer 23

Question 24

Recall features of hypothyroidism.

Answer 24

Question 25

Recall the causes of primary and secondary hypothyroidism.

Answer 25

Question 26

Describe cretinism.

Answer 26

Question 27

Describe myxedema.

Answer 27

Question 28

Describe thyroiditis.

Answer 28

Question 29

Recall Hashimoto’s Thyroiditis

Answer 29

Question 30

Recall Iatrogenic and drug-induced hypothyroidism.

Answer 30

Question 31

Recall the cells of the parathyroid glands.

Answer 31

Question 32

Recall the function and regulation of parathyroid glands.

Answer 32

Question 33

Recall the features of hyperparathyroidism.

Answer 33

Question 34

Recall primary and secondary parathyroidism. .

Answer 34

Question 35

Recall examples of the genetic basis of hyperparathyroidism.

Answer 35

• Most common cause of primary hyperparathyroidism is a parathyroid adenoma which is benign but can advance to cancer if left untreated
• Primary hyperparathyroidism is one of the most common endocrine disorders, and an important cause of hypercalcemia
• Examples of genetic basis:
  
  • A pericentromeric inversion of chromosome 11 involving the cyclin-D1 an PTH genes - leading to overexpression of cyclin-D1 in chief cells

Question 36

Describe hypoparathyroidism and its symptoms.

Answer 36

• Surgically induced hypoparathyroidism occurs with inadvertent removal of the parathyroid glands during thyroidectomy, can be mistaken for lymph nodes during neck surgery in ‘head & neck cancer’ patients
• Autoimmune hypoparathyroidism may accompany a long-term infection
• Extremely rare genetic conditions or congenital absence of parathyroid glands can occur in conjunction with other malformations

Question 37

Recall drugs for parathyroid diseases.

Answer 37