Week 11: Chp 43: Hypothyroidism Flashcards
The release of thyroid hormone is under the control of what?
-the anterior pituitary gland (secretion of TSH) and
-the hypothalamus (secretion of TRH)
>disorders affecting either of these structures can result in hypothyroidism
Hypothyroidism is largely associated with what?
-autoimmune disease, thyroid surgery, or radioactive iodine therapy used in the treatment of hyperthyroidism
What is the most common type of hypothyroidism?
Hashimoto’s thyroiditis
-caused by an autoimmune response that leads to destruction of the thyroid gland by immunological processes
Hashimoto’s Thyroiditis
caused by an autoimmune response that leads to destruction of the thyroid gland by immunological processes
-most common type of hypothyroidism
Hypothyroidism can also be associated with what deficiencies?
iodine and tyrosine deficiencies
-because they are needed for the synthesis of thyroid hormone, but rarely observed in US because of the use of iodized salt
Other causes of Hypothroidism
congenital thyroid disorders, autoimmune thyroid destruction, and thyroid cancer
Hypothyroidism is a major cause of what?
Goiter (enlargement of the thyroid gland)
-and develops secondary to thyroid gland hypertrophy in an attempt to produce normal amounts of T3 and T4
Hypothyroidism occurs most often in who?
in women between the ages of 30 and 60 and incidence increases with age
What is the hallmark of hypothroidism?
decreased metabolism
-affects most body systems
Primary Vs Secondary Vs Tertiary Hypothyroidism
- Primary; develops as a result of a disorder of the thyroid itself
- Secondary; is caused by a disorder of the anterior pituitary gland
- Tertiary: due to a disorder of the hypothalamus; lack of TRH from the hypothalamus
The hypometabolic state is characterized by what manifestations?
- decreased energy
- increased sleep
- fatigue
- weight gain
- decreased appetite
- susceptibility to cold temperatures
Patients with hypothyroidism may develop what condition?
myxedema
-a condition resulting from an increased deposition of glycosaminoglycans (a type of polysaccharide) in cells and tissues
Myxedema; The increased deposition of glycosaminoglycans causes what?
- an osmotic edema and fluid collection that is associated with a generalized non-pitting edema
- cardiac alterations secondary to myxedematous changes include decreased contractility, cardiac enlargement, pericardial effusion, decreased pulse, and decreased cardiac output
- decreased gastrointestinal activity results in constipation and abdominal distension
- skin changes may result over time secondary to cold intolerance, and a lack of sweating may leave the skin dry and coarse
- hair becomes thin and fragile, and hair loss occurs
Myxedema related to hypothyroidism, how a patient presents
- facial puffiness
- hair dry, coarse, thin, and fragile
- lateral eyebrows thin
- periorbital edema (bags under eyes)
- skin dry and coarse due to lack of sweating
The diagnosis of hypothyroidism can be confirmed through what?
analysis of laboratory data, including T3, T4, and TSH
- if the etiology is primary hypothyroidism, the TSH level is elevated as a result of the feedback system to the hypothalamus and anterior pituitary gland caused by low circulating levels of thyroid hormones (T3 and T4)
- In secondary or tertiary, the TSH may be high or near normal because the disorder is a result of pathophysiology in the anterior pituitary gland or hypothalamus
- When Hashimoto’s thyroiditis is suspected, an evaluation of anti-thyroid antibodies should be performed
Laboratory Tests for thyroid disorders
- Free T3 (triiodothyronine)
- Total T3 (triiodothyronine)
- Free T4 (thyroxine)
- Total T4 (thyroxine)
- TSH (thyroid-stimulating hormone)
Thyroid Disorders Lab tests: Free T3
Normal Range: 2.6- 4.8 pg/mL
Significance: decreased in hypothyroidism; increased in hyperthyroidism
Thyroid Disorder Lab Tests: Total T3
Normal Range: 70 to 204 ng/dL
Significance: Decreased in hypothyroidism, Increased in hyperthyroidism
Thyroid Disorder Lab Tests: Free T4
Normal Range: 0.8- 1.5 ng/dL
Significance: decreased in hypothyroidism, increased in hyperthyroidism
Thyroid Disorder Lab Tests: Total T4
Normal Range: 4.6- 12 mcg/dL
Significance: Decreased in hypothyroidism, increased in hyperthyroidism
Thyroid Disorder Lab Tests: TSH (thyroid-stimulating hormone)
Normal range: 0.4- 4.2 micro-international units/ mL
Significance: increased in primary hypothyroidism, decreased in secondary and tertiary hypothyroidism, decreased in primary hyperthyroidism, increased in secondary and tertiary hyperthyroidism
Primary Treatment for hypothyroidism
replacement of thyroid hormone
-most commonly prescribed is levothyroxine (Synthroid)
Medication: levothyroxine (Synthroid)
most commonly prescribed medication for hypothyroidism
- started at a low dose and increased as needed to treat symptoms of hypothyroidism
- taken in the morning because thyroid hormone affects metabolism
- replacement therapy is a lifelong regimen, and important to take at the same time everyday
- sudden increases in cardiac rate and contractility are secondary to the medication
Why is levothyroxine a safety alert for patients with a history of cardiovascular disease?
in patients with a history of cardiovascular disease, the increases in dosage of levothyroxine are made cautiously because sudden increases in cardiac rate and contractility secondary to the medication may lead to angina or congestive heart failure
Complications: Most severe type of hypothyroidism
myxedema coma
- characterized by hypoxia and carbon dioxide retention (secondary to hypoventilation), fluid and electrolyte imbalances, and hypothermia
- because of significant decreases in cardiac function, the patient is bradycardic and hypotensive
- hypoglycemia and hyponatremia develop
- significant hypothermia during times of myxedema crises, these patients are sensitive to sedatives, analgesics, and anesthetics agents because metabolism of these medications is significantly slowed, leading to accumulation in the body
Why should patients with hypothyroidism who are receiving sedatives, hypnotics, or narcotics require close observation?
because the metabolism of the medication is slower, and respiratory compromise may occur with normal dosages
-the dose, as well as the interval between doses, may need to be adjusted in the patient with severe hypothyroidism
Treatment of myxedema coma
aimed at replacing thyroid hormone and supportive measures
Clinical Manifestations observed with hypothyroidism are related to?
the decreased metabolic rate of most body tissues
- bradycardia
- decreased respiratory rate
- hypothermia
- weight gain despite decreased caloric intake
- elevated serum cholesterol secondary to decreased liver metabolism
- increased sleeping
- weakness and muscle aches
- anorexia
- constipation
- cold intolerance
- decreased in libido
Clinical Manifestations not linked to decreased metabolism
-development of goiter or generalized edema
>because of the decreased levels of thyroid hormone, TSH from the anterior pituitary gland may cause hyperplasia (an increase in the amount of organ tissue) of the thyroid gland leading to goiter (enlargement if the thyroid gland)
-while cellular metabolism decreases, energy is decreased, and metabolites such as proteins and sugars accumulate inside cells
-while these metabolites build up inside the cell, myxedema develops and is generalized by nonpitting edema, particularly in the hands, in the feet, between the shoulder blades, and around the eyes
-edema of the tongue and around the larynx results in changes in speech resulting in a husky tone
Nursing Diagnoses
- decreased cardiac output r/t decreased heart rate and decreased contractility secondary to impaired cardiac metabolism
- altered nutrition greater than body requirements r/t decreased cellular metabolism secondary to decreased thyroid hormone activity
- fluid volume excess r/t accumulation of mucinous edema secondary to altered cellular metabolism
Nursing Assessments
- oxygen saturation
- vital signs
- serum calcium levels
- daily weight
- skin texture, color, and turgor
- bowel elimination
Assessments: Oxygen Saturation
severe hypothyroidism may impair respiratory function, leading to decreased ventilation, which results in lower oxygen saturation
Assessment: Vital Signs
decreased body temperature, heart rate, respiratory rate, and blood pressure are secondary to the hypometabolic state caused by thyroid hormone deficit
Assessment: Serum Calcium Levels
in patients with hypothyroidism secondary to surgical resection/removal of the thyroid gland, damage or removal of parathyroid tissue may lead to decreased serum calcium levels
Assessment: Daily weight
decreased cellular metabolism may result in weight gain
Assessment: Skin texture, color, and turgor
skin changes are associated with decreased sweating and oil production and are secondary to a hypometabolic state
-with severe hypothyroidism, myxedema may develop linked to deposition of metabolites under the skin
Assessment: Bowel elimination
patient is at increased risk of constipation secondary to decreased gastrointestinal mobility
Nursing Actions
- administer thyroid replacement therapy at the same time everyday
- administer narcotics and sedatives with caution
- provide warming blankets as needed
- turn patient and promote skin integrity
Actions: administer thyroid replacement therapy at the same time everyday
lifelong thyroid hormone replacement is required in patients with hypothyroidism to increase metabolic activities of most body systems
-to mimic the normal circadian rhythm, Synthroid (levothyroxine) is administered in the morning
Actions: Administer Narcotics and Sedatives with caution
because of decreased metabolism on medication, secondary to hypothyroidism, the patient must be monitored closely for signs of overmedication such as decreased respiratory rate or difficulty arousing the patient after medication administration
Actions: Provide warming blankets as needed
decreased metabolism results in decreased energy production and cold intolerance
-patients should avoid warming too quickly because it can result in vasodilation and hypotension
Actions: Turn patient and reposition to promote skin integrity
because of myxedema, the skin integrity is altered requiring special actions to prevent pressure
Nursing Teaching
- immediately report chest pain or chest discomfort
- take thyroid replacement hormones as prescribed; must be taken daily
- sigs of hypothyroidism and hyperthyroidism
Teaching: Immediately report chest pain or chest discomfort
cardiovascular disease may develop in patients with hypothyroidism
-because of the decreased metabolism of cholesterol, patients with hypothyroidism are at a greater risk of elevated cholesterol levels
Teaching: take thyroid replacement hormones as prescribed; must be taken daily
thyroid hormone replacement is required for metabolic activities
-increasing the dose of medication without prescriber input may lead to accelerated cardiovascular function that the heart is unprepared to tolerate because of the long-term effects of hypothyroidism
Teaching: Signs of hypothyroidism and hyperthyroidism
it is important that the patient and family are able to detect early signs of both hypothyroidism (the underlying disorder that could progress to myxedema) and hyperthyroidism (secondary to thyroid hormone supplementation)
Evaluating Care Outcomes
can achieve normal thyroid function by complying with the prescribed therapy
- vital signs within normal limits, increased energy, stable weight, and normal skin turgor and texture are indicative of thyroid health
- during periods of stress, such has invasive procedures, an adjustment in thyroid medications may be indicated
- providers should be aware of the hypothyroidism, especially when prescribing sedatives, narcotics, or anesthetic agents
