Pharmacology: Thyroid II

Question 1

What are the possible treatments for myxedema?

Answer 1

Myxedema = Hypothyroidism

• Thyroid USP: dried, defatted thyroids from pig & sheep
  unpredictable strength
• Thyroglobulin
• Sodium levothyroxine: T4 = drug of choice
• Sodium liothyronine: T3; used for myxedema coma
• Liotrix

Question 2

What are drug treatment options for hyperthyroidism? MOA?

Answer 2

Thioamides:

Propylthiouracil

Methimazole

Carbimazole (in UK)

–> MOA: inhibiting Thyroid Peroxidase ==> prevents iodizatiion of thyroglobulin and production of T3 and T4

Question 3

What are the toxicities of thioamides?

Answer 3

• *Caution in pregnancy:**
• Both PTU and methimazole cross placenta; use lowest possible dose
• Thioamides cross into mother’s milk

Rare cases of agranulocytosis

Question 4

How is a “thyroid storm” treated?

Answer 4

Thyroid storm is due, in large part, to supersensitization of b-adrenergic receptors
–> Treat immediately with b-blockers:
Propanolol
Atenolol

–> Long term treatment with thioamides (PTU, methimazole)

Question 5

What is the premise of readioactive iodide treatment?

Answer 5

In theory, in the case of toxic nodular adenoma, the adenoma takes up the radioactive iodine while the quiescent normal tissue takes up less

–> In practice, it usually desetroys most of the thyroid

–> Must replace loss of thyroid hormone with levothyroxine

**NEVER use ¹³¹I during pregnancy!*

Question 6

What is the drug of choice to treat hyperthyroidism?

Answer 6

Radioactive iodine

Question 7

What is the treatment for hypoparathyroidism?

Answer 7

Problem: Low PTH (low serum Ca, high serum phosphate)
- can lead to tetany, convulsions, and death

Treatmetn:

1,25(OH)₂D₃ and dietary Ca²⁺ supplement

Question 8

What is the treatment for pseudohypoparathyroidism?

Answer 8

Problem: PTH is elevated, but Ca²⁺ is lwo

• -> often the G-protein G_s is low or abnormal
• -> PTH fails to stimulate 1a hydroxylase activty in the kidney

Treatment: 1,25(OH)₂D₃

Question 9

What is the treatmet for Rickets?

Answer 9

Problem: lack of sufficient sunlight –> insufficient D3 to make 1,25(OH)₂D₃
- Increased PTH –> Ca removal from bones –> bones become soft

Treatment: sunlight
food supplemented with vit. D2 or D3

Question 10

What is the treatment for Vitamin D-Dependent Rickets?

Answer 10

Problem: abnormal 1a-hydroxylase in kidney

• autosomal recessive
• sun exposure is not effective

Treatment: 1,25(OH)₂D3

Question 11

What is the treatment for drug-induced osteopenia?

Answer 11

Problem - Certain drugs interfere with Ca absorption from gut

• pheytoin
• phenobarbital
• glucocorticoids

Treatment: Vitamine 25(OH)D3, D2, or D3

Question 12

What is the treatment for Paget’s Disease?

Answer 12

Problem: overactivity of osteoclasts leads to abnormal restructuring of bone - patients prone to compression fractures

Treatment: Calcitonin or bisphosphonates

Question 13

What are examples of bisphosphonates?

Answer 13

Elondronate

Risedronate

Sodium Etidronate

Pamidronate

Ibandronate

Zoledronic acid

Question 14

What are the treatment options for post-menopausal osteoporosis?

Answer 14

Estrogen

SERMs (raloxifene)

Bisphosphonates (Alendronate)

Teriparatide (active portion of PTH) - daily subcut. injection

Denosumab - anti-RANKL monocloonal Ab (mimics OPG)