Thyroid

Question 1

Thyroid Hormone Forms

Answer 1

Triiodothyronine (T3) - Active

Thyroxine (T4) - Inactive

T3 more potent than T4

Question 2

Hypothalamus

Answer 2

Secretes thyrotropin-releasing hormone (TRH)

Stimulates the anterior pituitary

Question 3

Anterior Pituitary Gland

Answer 3

Stimulation of thyrotropic cells secretes the release of thyroid stimulating hormone (TSH)

Question 4

Thyroid Gland

Answer 4

Stimulates 2 effects:

Synthesis and secretion of thyroid hormones

Trophic effect - increases thyroid gland growth

Question 5

Negative Feedback Loop

Answer 5

High amounts of thyroid hormone in the bloodstream inhibit the secretion of both TRH and TSH

Question 6

Hypothyroidism

Answer 6

Endocrine gland hyposecretion results in hormone deficiency

• Hashimoto’s thyroiditis
• Severe iodine deficiency
• Congenital hypothyroidism

Question 7

Hyperthyroidism

Answer 7

Endocrine gland hypersecretion results in hormone excess

• Graves’ disease
• Thyroid nodules
• Postpartum thyroiditis

Question 8

Hypothyroidism Symptoms

Answer 8

Weight gain

Cold intolerance

Weakness

Fatigue

Hair loss

Decreased libido

Constipation

Myxedema coma

Question 9

Hyperthyroidism Symptoms

Answer 9

Weight loss

Heat intolerance

Sweating

Increase heart rate (tachycardia)

Irritability

Nervousness

Exopthalmos (Graves’ Disease)

Question 10

Hypothyroidism Treatment

Answer 10

Thyroid hormone replacement therapy

Question 11

Levothyroxine Brand Name

Answer 11

Synthroid

Levoxyl

Levothroid

Unithroid

Question 12

Levothyroxine MOA

Answer 12

Acts as synthetic thyroid hormone of thyroxine (T4)

Question 13

Levothyroxine Initial Dosing

Answer 13

Full replacement dose

• 1.6 mcg/kg/day using IBW
• Healthy, <50 yo adult

Partial replacement dose

• Start low 25-50 mcg daily
• Elderly, comorbidities (coronary artery disease)

Question 14

Levothyroxine Administration

Answer 14

• Take in the morning on an empty stomach
  
  • 30-60 minutes before first meal of the day
• Take with a full glass of water
• Separate from other medications by 4 hours
  
  • Antacids
  • Iron supplements
  • Multivitamins

Question 15

Levothyroxine Side Effects

Answer 15

Tachycardia

Palpitations

Sweating

Weight loss

Arrhythmias

Irritability

Decreased bone mineral dansity

Question 16

Levothyroxine Precautions/Warnings

Answer 16

Cardiac arrhytmias and cardiac arrest

*Use caustion in patients with underlying cardiac disease/older patients*

Question 17

Levothyroxine Contraindications

Answer 17

Recent acute MI

Uncorrected adrenal insufficiency

Question 18

Levothyroxine Follow-Up and Monitoring

Answer 18

• Symptomatic improvement within about two weeks
  
  • May take 6-8 weeks for normalization of TSH levels
• TSH levels
  
  • Monitoring parameters throughout course treatment:
    
    • every 4-6 weeks until normalized
    • every 8-12 weeks after dose change
    • every 6-12 months thereafter (annual more common)

Question 19

Hyperthyroidism Treatment

Answer 19

Anti-thyroid medications

Radioactive iodine treatment

Surgical removal of thyroid gland