Repro-Endo: Thyroid / Parathyroid

Question 1

Levothyroxine / Triiodothyronine

Answer 1

• T₄ analog (Thyroxine replacement) / T₃ analog
• Binds to nuclear receptors
• Increased Protein synthesis and Metabolic rate
• Increased Beta-receptor Increased sensitivity to Catecholamines
• Tx: Hypothyroidism / Myxedema
• SE: Hyperthyroidism (Tachy, Heart failure, Sweating, Tremor, Arrhythmias, Diarrhea)

Question 2

Methimazole, Propylthiouracil (PTU)

Answer 2

• Thionamides
• Inhibits Thyroid Peroxidase –> Blocking Synthesis
• Propylthiouracil (PTU) also inhibits Peripheral conversion of T₄ –> T₃ by blocking 5’-deiodinase
• PTU avoided as first line treatment
• PTU used during First Trimester in pregnancy (Teratogenic effects)
• Tx: Hyperthyroidism, 3 Ps of PTU
• SE: Rash, Urticaria, Fever, Nausea, Agranulocytosis, Thrombocytopenia, Acute Hepatic necrosis, Vasculitis, Hepatotoxicity (Propylthiouracil) Possible Teratogen (Methimazole)

Question 3

Iodine and Radioiodine

Answer 3

• Inhibits Thyroid Hormone release
• ¹³¹I concentrated in the Thyroid gland and emits Beta and Gamma XRT
• Drug of choice for destroying Toxic Adenoma
• NEVER USE w/ Pregnant women
• Tx: Thyroid Storm and Before Thyroidectome (prevents Thyroid Storm), Hyperthyroidism, Adjunctive Tx for some Thyroid cancers
• SE: Dysgeusia (metalic taste), Excessive salvation, Diarrhea, Rash

Question 4

Bisphosphonates

(Alendronate)

Answer 4

• Stabilizes bony matrix
• Coats hydroxyapatite to prevent Osteoclasts from Resorbing bone
• Tx: Postmenopausal Osteoporosis, Paget disease
• SE: Heartburn, Erosive esophagitis, Stomach upset, Joint/Back pain, Osteonecrosis of the Jaw

Question 5

Calcitonin

Answer 5

• Lowers Serum Calcium
• Mild analgesic properties for Bone pain
• Intranasal / Subcutaneous
• Tx: Hypercalcemic states
• SE: Runny nose, and Nasal discomfort, Flushing

Question 6

Calcitriol

Answer 6

• Activated form of Vitamin D
• Increases Calcium absorption from Intestines
• Tx: Hypocalcemia, Vit. D replacement in Pts. w/ End-Stage Renal Disease
• SE: Vit. D. Intoxication: Hypercalcemia, Polyuria, Weakness, Headache, Somnolence, and Constipation

Question 7

Rx for Hypothyroidism?

Answer 7

Levothyroxine (T₄)

Question 8

Rx for Hyperthyroidism?

Answer 8

1st: Methimazole
2nd: PTU (Propylthiouracil)

Pregnancy: 1st Trimester = PTU, 2nd - 3rd = Methimazole

Question 9

Rx for Thyroid Storm?

Answer 9

¹³¹I or Radioiodine

Question 10

Rx for Postmenopausal Osteoporosis?

Answer 10

Bisphosphonates

(Alendronate)

Question 11

Rx for Paget Disease to reduce bone turnover?

Answer 11

Bisphosphonates

(Alendronate)

Question 12

Rx for Hypercalcemic states?

Answer 12

Calcitonin

MISHAP

• Malignancy
• Intoxication w/ Vit. D
• Sarcoidosis
• Hyperparathyroidism
• Alkali (Mikl-alkali syndrome)
• Paget Disease

Question 13

Rx for Hypocalcemia?

Answer 13

Calcitriol

Question 14

Rx for End-Stage Renal Disease?

Answer 14

Calcitriol

Question 15

Thyroglobulin

Answer 15

• Rx for Hypothyroidism
• Potency of each preparation varies
• Thyroglobulin is a protein produced by thyroid cells (both normal and cancerous cells). After removal of the thyroid gland, Thyroglobulin can be used as a “cancer marker.”

Question 16

Sodium Liothyronine

Answer 16

• Tx for Hypothyroidism
• Short acting w/ Rapid onset
• A synthetic form of natural T3 hormone with same actions as natural product; thyroid hormone raises basal metabolic rate, increases utilization and mobilization of glycogen store, and promotes gluconeogenesis
• Tx: Hypothyroidism, Nontoxic goiter, Myxedema, Myxedema coma

Question 17

Lugol’s Solution

(KI and I₂)

Answer 17

• a solution of elemental iodine and potassium iodide in water
• It was also used at one time as a first line treatment for Hyperthyroidism, as the administration of pharmacologic amounts of iodine leads to temporary inhibition of iodine organification in the thyroid gland, a phenomenon called the Wolff-Chaikoff effect.

Question 18

Mechanism of PTH?

Answer 18

• PTH increases plasma Ca²⁺
• Stimulates adenylyl cyclase in target tissues
• Elevated cAMP inhances syn. of 1,25(OH)₂D₃
• Increasing bone resorption by activating Osteoblast –> Osteoclast and Stimulating Ca²⁺ transport from bone to extracellular fluids
• Increases the synthesis of 1,25(OH)₂D₃ at the lvl of the Kidney
• Increases Renal tubular reabsorption of Ca²⁺

Question 19

Mechanism of 1,25(OH)₂D₃

Answer 19

• 1,25 dihydroxycholecalciferol
• 7 dehydrocholesterol is converted to Cholecalciferol (D₃) by UV light at the skin
• D₃ is converted to 25(OH)D₃ in the Liver
• 25(OH)D₃ converted to 1,25(OH)₂D₃ (calcitriol) in the Kidney
• PTH stimulates 1α-hydroxylase, is the Kidney’s converting enzyme.
• Increases plasma Ca²⁺
• Increasing the synthesis of Ca²⁺ binding transport protein in the Mucosal cells of the gut –> Increaseing absorption
• Increasing Ca²⁺ transport from Bone to Extracellular fluids (in large doses)

Question 20

Mechanism of Calcitonin?

Answer 20

• Decreases plasma Ca²⁺
• Decreasing bone reabsorption by inhibiting activity of osteoclasts
• Decreasing tubular reabsortpion of Ca²⁺

Question 21

Rx for Hypoparathyrodism?

Answer 21

• Hypocalcemia
• Hyperphosphatemia
• Tx: Dietary calcium and 1,25(OH)₂D₃
• PTH and Calcium gluconate mabe be used following surgical parathyroidectomy to prevent Hypocalemic tetany

Question 22

Rx for Pseudohypoparathyrodism?

Answer 22

• PTH lvls are Normal or Elevated
• Serum Ca²⁺ is low
• End organs are insensitive to PTH
• Often abnormal Gs, the transducer that links PTH receptor to Adenylyl cyclase
• Tx: 1,25(OH)₂D₃ can correct Hypocalcemia, but it does not always improve Bone disease

Question 23

Rx for Rickets and Osteomalacia?

Answer 23

• Inadequate miniralization of Bone matrix
• Lack of exposure to sunlight, resulting in impaired vitamin D₃ synthesis in the skin
• Supplementing food and Vit. D₂ has greatly reduced the incidence
• Tx: Administer Vit. D₂ or D₃

Question 24

Rx for Vit. D-dependent Rickets?

Answer 24

• Autosomal recessive does not respond to Vit. D admin.
• Defect belived to be in the 1α-hydroxylase enzyme w/in the Kidney
• Tx: 1,25(OH)₂D₃

Question 25

Rx for Drug-induced Osteopenia?

Answer 25

* The anticonvulsant drugs, Phenytoin, Phenobarbital, and Corticosteroids, suppress intestinal Ca²⁺ absorption w/ Secondary Hyperparathyroidism (elevated PTH) * High doses of corticosteroids inhibit Osteoblast diff. and Collagen syn. --\> decreased bone mass * Tx: 25(OH)D₃, D₂, or D₃ improve symptoms of Anticonvulsant-induced Osteomalacia (Osteopenia)

Question 26

Rx for Paget's Disease?

Answer 26

* Overactive Osteoclast activity in bone resulting in Deminieralization of Osteoid tissue * Painful, Multiple bone compression fractures * Tx: Calcitonin via Nasal spray, Sodium Etidronate (bisphosphonate), also Alendronate and Risedronate, and even Ibandronate.

Question 27

Rx for Postmenopausal Osteoporosis?

Answer 27

* Abnormal, rapid loss of bone, predisposing postmenopausal women to Fracture * Tx: Estrogen replacement therapy w/ increased risk of Heart disease, Breast cancer, and Uterine cancer w/ HRT * SERM - Raloxifene is safer * Bisphosphonates: Alendronate, Risedronate, Ibandromate, or Zoledronic acid * Teriparatide (Human PTH_1-34) is effective for treating osteoporosis --\> stimulates new bone growth and reduces vertebral fracture risk by 65%, injected daily

Question 28

Rx for Vitamin D intoxication?

Answer 28

* Hypercalcemia leading to Ca²⁺ deposition in soft tissues * Tx: Stop Vit. D administration, Administer Glucocorticoids, such as **Prednisone --\> Block GI absorption of Ca²⁺**

Question 29

Rx Primary Hyperparathyroidism?

Answer 29

* Commonly Adenoma * Severe Hypercalcemia, Hypophosphatemia, Prominent bone resoprtion, Soft Tissue calcification, Elevated 1,25(OH)₂D₃ and Nephrolithiasis * Tx: Surgical removal of Adenoma