Hypothyroidism

Question 1

What is hypothyroidism?

Answer 1

A deficiency of thyroid hormone that causes a general slowing of the metabolic rate

• 4% of US population has mild hypothyroidism, w/ 0.3% having more severe disease
• more common in women

Question 2

Patho

Answer 2

• Primary: related to destruction of thyroid tissue or defective hormone synthesis
• Secondary: Related to pituitary disease with decreased thyroid-stimulating hormone (TSH) secretion or hypothalamic dysfunction w/decreased thyrotropin-releasing hormone (TRH) secretion
• can be transient, related to thyroiditis or discontinuing thyroid hormone therapy

Question 3

Causes of hypothyroidism?

Answer 3

• Iodine deficiency most common
• in US common cause of primary is atrophy (wasting away) of thyroid gland. This is the end result of Hashimoto’s thyroiditis or Graves disease
• autoimmune diseases destroy thyroid gland

Question 4

May also develop as a result of treatment of?

Answer 4

Hyperthyroidism, specifically thyroidectomy or radioactive iodine (RAI) therapy.
- Drugs such as amiodarone (Cordarone), which contains iodine or lithium that block hormone production, can cause hypothyroidism

Question 5

Hypothyroidism that develops in infancy (cretinism) is caused by?

Answer 5

Thyroid hormone deficiences during fetal or early neonatal life

Question 6

Clinical manifestations of hypothyroidism

Answer 6

• vary depending on severity & duration of thyroid deficiency as well as patients age at onset of deficiency
• has systemic affects characterized by a slowing of body processes
• fatigue
• lethargic
• personality and mental changes including impaired memory, slowed speech, decreased initiative and somnolence
• many appear depressed
• weight gain
• decreased CO, contractility, and coronary atherosclerosis
• anemia
• increased serum cholesterol & triglyceride levels and the accumulation of mucopolysaccharides in the intima of small blood vessels can result in coronary atherosclerosis
• decreased GI motility & achlorhydria (absence or decreased secretion of hydrochloric acid
• constipation may progress to obstipation
• older adult: fatigue, cold and dry skin, hair loss, constipation, hoarseness, and cold intolerance
• myxedema: puffiness, facial and periorbital edema, and masklike effect
• altered self image

Question 7

Hypothyroidism complications

Answer 7

The mental sluggishness, drowsiness, and lethargy may progress gradually or suddenly to a notable impairment of consciousness or coma. This situation, termed myxedema coma, consititutes a medical emergency

• myxedema coma can be precipitated by infection, drugs (opioids, tranquilizers, and barbiturates), exposure to cold, and trauma. characterized by subnormal temperature, hypotension, and hypoventilation
• For the pt to survive, vital functions must be supported and IV thyroid hormone replacement administered

Question 8

Hypothyroidism diagnostic studies

Answer 8

• Serum TSH and free thyroxine (FT4) are most reliable indicators of thyroid function
• Serum TSH levels help determine the cause. If high, the defect is in the thyroid; if low, it is in the pituitary or hypothalamus
• Presence of thyroid antibodies suggests an autoimmune origin or the hypothyroidism
• Elevated cholesterol and triglycerides, anemia, and increased creatine kinase can occur

Question 9

Hypothyroidism interprofessional care

Answer 9

• goal is restoration of the euthyroid state as safely & rapidly as possible w/hormone therapy
• low calorie diet indicated to promote weight loss or prevent weight gain
• Levothyroxine (Synthroid) drug of choice. In young pt the maintenance replacement dosage is adjusted according to the pt’s response and lab findings.
• initial doses are low to avoid increases in resting HR and BP
• pt w/compromised cardiac status, careful monitoring is needed when starting and adjusting the dosage because the usual dose may increase myocardial oxygen demand, causing angina & cardiac dysrhythmias
• Levothyroxine has a peak action of 1-3 weeks. In the pt w/out side effects the dose is increased at 4-6 week intervals
• Liotrix: synthetic mix of levothyroxine (T4) and liothyronine (T3) in a 4:1 combination. Fast onset of action and a peak of 2-3 days, can be used in acutely ill pt’s