Week 3: Thyroid Goiter

Question 1

Why does a goiter develop?

Answer 1

• adaptive response to insure adequate thyroid hormone levels
• decrease in iodine availability leads to fall in T4 secretion
• compensatory rise in serum TSH
• stimulation of thyroid gland leads to
  1. thyroid growth: TSH and IGF-1 mediated
  2. preferential T3 secretion by thyroids
• relative T3 excess/T4 deficiency state

Question 2

sporadic non toxic goiter

Answer 2

• found in areas with plenty of iodine
• defect is similar, can be in thyroid peroxidase, or with I- intake, or anywhere along the way of making thyroid hormone

Question 3

Pathogenesis of toxic multi nodular goiter

Answer 3

• possible outcome of any longstanding goiter
• autonomous thyroid cells proliferate (function independent of TSH): mutations in TSH receptor that activate cAMP
• precipitated by exposure to iodine (Jod-Basedow), from acute load such as contrast studies or chronic from treatment of hyperthyroidism

Question 4

Therapy of goiter

Answer 4

1. Acute
   - antithyroid drugs (MMI or PTU)
   - beta blockers if indicated
2. Long term
   - render euthyroid
   - total thyroidectomy is treatment of choice
   - If not surgical candidate, 131-I