Hypothyroidism Flashcards
What is hypothyroidism?
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
Patho
- 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
Causes of hypothyroidism?
- 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
May also develop as a result of treatment of?
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
Hypothyroidism that develops in infancy (cretinism) is caused by?
Thyroid hormone deficiences during fetal or early neonatal life
Clinical manifestations of hypothyroidism
- 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
Hypothyroidism complications
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
Hypothyroidism diagnostic studies
- 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
Hypothyroidism interprofessional care
- 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
