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Endo > Pharma 2: Drugs For Thyroid And Parathyroid Disorders > Flashcards

Pharma 2: Drugs For Thyroid And Parathyroid Disorders Flashcards

1
Q

List the 5 steps of synthesis and release of thyroid hormones?

A

1- Iodide uptake.
2- Oxidation and iodination of tyrosine.
3- Coupling reaction.
4- Storage and release.
5- Peripheral conversion of T4 to T3.

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2
Q

What happens in the first step of synthesis and release of thyroid hormones, iodide uptake?

A

Iodine is actively taken up by the follicular cells under the influence of TSH.

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3
Q

What happens in the second step of synthesis and release of thyroid hormones, oxidation and iodination of tyrosine?

A

Iodide is oxidized to iodinium ion (I+) by thyroid peroxidase.
I+ combines with tyrosine (on surface of thyroglobulin) to form MIT and DIT.

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4
Q

What happens in the third step of synthesis and release of thyroid hormones, coupling reaction?

A

MIT + DIT = T3.
DIT + DIT = T4.
These reactions are catalyzed by thyroid peroxidase.

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5
Q

What happens in the fourth step of synthesis and release of thyroid hormones, storage and release?

A

T3 and T4 formed on surface of thyroglobulin is transported to inner side of follicle for storage as thyroid colloid.
They are released by proteolysis and exocytosis under influence of TSH.

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6
Q

What happens in the fifth step of synthesis and release of thyroid hormones, peripheral conversion of T4 to T3?

A

More T4 is released than T3.
Circulating T4 is converted to T3 by idothyronine 5’-deiodinase.

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7
Q

Which 3 drugs block the conversion of T4 to T3 in the periphery?

A

1- Propythiouracil.
2- High dose of propranolol.
3- Glucocorticoids.

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8
Q

Which thyroid hormone is more active?

A

T3 is 5 times more active than T4.

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9
Q

List the 3 proteins thyroid hormones are bound to?

A

1- Thyroxine binding globulin (TBG).
2- Thyroxine binding prealbumin.
3- Albumin.

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10
Q

What inactivates thyroid hormone?

A

Deiodination, decarboxylation and conjugation mainly in the liver.

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11
Q

List the symptoms of hyperthyroidism?

A

1- Intolerance to heat.
2- Fine, straight hair.
3- Bulging eyes.
4- Facial flushing.
5- Enlarged thyroid.
6- Tachycardia.
7- High systolic BP.
8- Breast enlargement.
9- Weight loss.
10- Muscle wasting.
11- Tremors.
12- Finger clubbing.
13- High diarrhea.
14- Localized edema.
15- Menstrual changes (amenorrhea).

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12
Q

List the symptoms of hypothyroidism?

A

1- Intolerance to cold.
2- Receding hairline.
3- Facial and eyelid edema.
4- Dull-blank expression.
6- Hair loss.
7- Extreme fatigue.
8- Thick tongue.
9- Apathy.
10- Anorexia.
11- Dry skin.
12- Brittle hair and nails.
13- muscle ache and weakness.
14- Weight gain.
15- Bradycardia.

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13
Q

List 3 drugs used for hypothyroidism?

A

1- Levothyroxine (T4).
2- Liothyronine (T3).
3- Liotrix (T4/T3 combination).

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14
Q

Which drug for hypothyroidism is preferred? And why?

A

Levothyroxine (T4) is preferred over T3 (liothyronine) or T3/T4 combination products (Liotrix) for the treatment of hypothyroidism.
Because it is better tolerated than T3 preparations and has a longer half-life.

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15
Q

What is levothyroxine (T4) absorption?

A

-Well absorbed from the stomach and small intestine (80% absorption).
- Absorption increases on taking on an empty stomach.

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16
Q

Levothyroxine (T4) is available as which preparations?

A

1- Tablets and liquid-filled capsules.
2- Lyophilized powder for injection.

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17
Q

What is the dosage of levothyroxine (T4)?

A

Is dosed one daily, and steady state is achieved in 6 to 8 weeks.

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18
Q

What is the adverse effects of Levothyroxine (T4)?

A

Toxicity is directly related to T4 levels and manifests as nervousness, palpitations and tachycardia, heat intolerance, and unexplained weight loss.

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19
Q

List the the available preparations for liothyronine (T3)?

A

Tablets and an injectable form.

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20
Q

When is liothyronine used?

A

When a more rapid onset of action is desired, such as myxedema coma. (Emergency settings).

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21
Q

Why is liothyronine less desirable for chronic replacement therapy?

A

1- More frequent dosing.
2- Higher cost.
3- Risk of arrhythmia*.

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22
Q

List 8 uses of thyroid hormones?

A

Mainly used as a supplement in hypothyroidism in:
1- Children - Cretinism.
2- Adult hypothyroidism.
3- Myxoedema (non-pitting edema).
4- Simple or non-toxic goiter (swelling of the thyroid even though thyroid hormone levels are normal).
5- Myxoedema coma.
6- Subclinical hypothyroidism (normal T3 and T4, high TSH).
7- Nodular goiter.
8- Papillary carcinoma of thyroid.

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23
Q

List the 4 classes of drugs used for hyperthyroidism?

A

1- Hormone synthesis inhibitors (antithyroid drugs).
2- Hormone release inhibitors.
3- Destruction of thyroid tissue.
4- Ionic inhibitors.

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24
Q

List 3 examples of hormone synthesis inhibitors (antithyroid drugs)?

A

1- Propyltiouracil.
2- Carbimazole.
3- Methimazole.
(Carbimazole gets converted into methimazle).

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25
Q

List examples of hormone release inhibitor drugs used in hyperthyroidism?

A

Iodides (Lugol’s iodine, Sodium iodide, Potassium iodide).

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26
Q

List an example of drugs that cause destruction of thyroid tissue used in hyperthyroidism?

A

Radioactive iodine.

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27
Q

List the 3 examples of ionic inhibitor drugs used in hyperthyroidism?

A

1- Thiocynates.
2- Perchlorates.
3- Nitrates.

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28
Q

What is MOA of antithyroid drugs?

A

Inhibits the synthesis of thyroid hormones.
They inhibits the enzyme thyroid peroxidase,
Thus inhibit:
- Oxidation and iodination of tyrosine residue.
- Coupling reaction.

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29
Q

Which antithyroid drug also inhibits the peripheral conversion of T4 to T3?

A

Propylthiuracil (PTU).

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30
Q

What are the pharmacokinetics of antithyroid drugs?

A

Rapidly absorbed orally.
Readily crosses the placenta and enters milk.
Excreted in urine as inactive conjugated form.

31
Q

Which antithyroid drugs are used during the 1st trimester of pregnancy?

A

PTU is preferred.
Methimazole is avoided due to risk of teratogenicity.

32
Q

Which antithyroid drug is used for the remainder of pregnancy? (After 1st trimester).

A

Methimazole is preferred.
Risk of PTU-associated liver failure in pregnancy.

33
Q

List the uses of antithyroid drugs?

A

1- To achieve spontaneous remission and control in:
- Grave’s disease.
- Toxic nodular goiter.
2- Used prior to radioactive iodine.
3- Pre-operative control of hyperthyroidism.
4- Thyroid storm.

34
Q

Which antithyroid drug is preferred for thyroid storm?

A

PTU, because it can inhibit peripheral conversion.

(PTU is preferred only during 1st trimester and for thyroid storm, otherwise mathimzaole is preferred).

35
Q

Why is methimazole preferred over PTU?

A

1- once daily dosing.
2- lower incidence of adverse effects.

36
Q

List 6 adverse effects of antithyroid drugs?

A

1- Skin rashes (most common).
2- Nausea, headache.
3- Pain and stiffness in the joints.
4- loss or greying of hair.
5- agranulocytosis (rare but serious reaction).
6- PTU is associated with hepatotoxicity.

37
Q

What should patients be instructed to immediately report when taking antithyroid drugs?

A

Patients should be instructed to immediately report the development of sore throat or fever and should discontinue their antithyroid drug and obtain a granulocyte count.

38
Q

What is the fastest acting agent used in treatment of hyperthyroidism?

A

Iodine and iodides.

39
Q

What is the MOA of iodine and iodides?

A

They inhibit the release thyroid hormones.

40
Q

What happens to the thyroid gland when given iodine?

A

The gland shrinks in size and becomes firm and less vascular.
The maximal effects occurs after 10-15 days of continuous therapy.

41
Q

What happens with iodine in continuous treatment?

A

There is loss of therapeutic effect.
(Thyroid constipation and thyroid escape).

42
Q

What happens to iodine in high concentrations?

A

In high concentration, iodine limits its own transport and acutely and transiently inhibits the synthesis of thyroid hormones (the Wolff-Chaikoff effect).

43
Q

List the 2 uses for iodides?

A

1- Pre-operative preparation before subtotal thyroidectomy (given 7-10 days pre-operatively to shrink the gland, make it firm and less vascular).
2- Thyroid storm (in conjunction with antithyroid and propranolol).

44
Q

List the adverse effects of iodides?

A

1-Hypersensitivity to iodine; angioedema and laryngeal edema.
2- Chronic intoxication causes ‘iodism’

45
Q

List examples of radioactive iodine?

A

I-127: stable isotope.
I-131, I-123, I-125: radioactive isotopes.

46
Q

What is the commonly used isotope for therapeutic and diagnostic purposes?

A

I-131.

47
Q

What does I-131 emit?

A

Emits y (gamma) and B (beta) particles.

48
Q

How is I-131 administered?

A

Take as sodium salt by oral route.

49
Q

What is the MOA of radioactive iodine?

A

The radioactive iodine is actively taken up by the follicular cells.
It emits B (beta) particles which destroys thyroid parenchyma.
There is negligible damage to adjacent tissue.

50
Q

List the 4 uses of radioactive iodine?

A

1- Grave’s disease.
2- In patients who cannot undergo thyroidectomy (elderly patients).
3- Patients with existing heart disease.
4- Toxic nodular goiter.

51
Q

List the advantages of radioactive iodine?

A

1- Risk of complications of surgery is avoided:
- No surgical scar.
- No injury to recurrent laryngeal nerve.
- No damage to parathyroid gland.
2- Cure is permanent.

52
Q

List the disadvantages of radioactive iodine?

A

1- Permanent hypothyroidism.
2- Delayed onset.
3- Cannot be used during pregnancy.
4- Avoided in young patients.

53
Q

List a drug that can be used as adjuvant therapy and for symptomatic treatment for hyperthyroidism?

A

Beta blockers (propranolol).

54
Q

What is the MOA and use of propranolol for hyperthyroidism?

A
  • Antagonize the sympathetic/adrenergic effects of thyrotoxicosis.
  • Reduce the tachycardia, tremor, and stare. And relieve palpitations, anxiety, and tension.
55
Q

What is the treatment for thyroid storm?

A

1- Supportive measures.
2- Antithyroid drugs - PTU is preferred (PTU impairs peripheral conversion of T4 > T4).
3- Oral iodides.
4- Beta-blockers (propranolol specifically).
5- Treatment of the under precipitating illness.
(Also glucocorticoids).

56
Q

What is the treatment of life-threatening hypercalcemia in primary hyperparathyroidism?

A

1- IV fluids (to dilute Ca in blood).
2- Bisphosphonates.
3- Calcitonin.
4- Cinacalcet.

57
Q

What is the most common cause of hypoparathyroidism?

A

Damage to the parathyroid glands (or their blood supply) during thyroid surgery.

58
Q

What is the treatment of hypoparathyroidism?

A

1- Oral calcium salts.
2- Vitamin D analogues.
3- PTH analogues.

59
Q

What is MOA of calcitonin?

A

Lowers plasma Ca2+ and phosphate concentrations in patients with hypercalcemia.
Calcitonin causes direct inhibition of osteoclastic bone resorption.

60
Q

How is calcitonin administered?

A

Through subcutaneous injection or nasal spray.

61
Q

What are the uses of calcitonin?

A

1- Hypercalcemia.
2- Disorders of increased skeletal remodeling, such as Paget disease.

62
Q

Which class of drugs mimc the stimulatory effect of Ca2+?

A

Calcimimetics.

63
Q

What is the MOA of calcimimetics?

A

They act on calcium-sensing receptor (CaSR) to inhibit PTH secretion by the parathyroid glands.

64
Q

What is the first and only approved Calcimimetics?

A

Cinacalcet.

65
Q

List the 2 uses of calcimimetics: cinacalcet?

A

1- Secondary hyperparathyroidism.
2- Hypercalcemia due to primary hyperparathyroidism or parathyroid carcinoma (as an alternative treatment to surgery).

66
Q

Which group of drugs are analogues of pyrophosphate?

A

Bisophosphonates.

67
Q

What is MOA of Bisphosphonates?

A

They act by direct inhibition of bone resorption.
Bisphosphonates concentrate at sites of active remodeling > released in the acid environment of the resorption lacunae > induce apoptosis in osteoclasts.

68
Q

List first generation Bisphosphonates?

A

Medronate, clodronate, and etidronate.

69
Q

List second generation Bisphosphonates?

A

Alendronate and pamidronate. (Osteoporosis)

70
Q

List third generation Bisphosphonates?

A

Risedronate, and zoledronate (for more dangerous conditions).

71
Q

With each generation of Bisphosphonates there is what change?

A

Increasing potency.

72
Q

List 5 uses of Bisphosphonates?

A

1- Post-menopausal osteoporosis.
2- Steroid-induced osteoporosis.
3- Paget disease.
4- Tumor-associated osteolysis.
5- Hypercalcemia.

73
Q

List adverse effects of oral Bisphosphonates?

A

Can cause heartburn, esophageal irritation, or esophagitis.

74
Q

What should patients taking oral Bisphosphonates do to avoid or reduce adverse effects?

A

Take it with a full glass of water at least 30 mins before breakfast.
Don’t lie down after taking it, remain upright.

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