Key Points
Hypothyroidism is a deficiency of thyroid hormones.
Approximately 9.6 million Americans have hypothyroidism (Carroll, 2009).
Hypothyroidism is more common in women than in men (Carroll, 2009).
Overview
Hypothyroidism is common in older adults and increases with age. Hypothyroidism often presents subtle, non-specific symptoms. (The American Thyroid Association, 2012).
There are four types of hypothyroidism:
• Primary, the most common due to disease of the thyroid. • Secondary, hypothyroidism due to disease in the pituitary. • Tertiary hypothyroidism, due to disease of the hypothalamus. • Subclinical hypothyroidism, an elevation of thyroid stimulating hormone (TSH) with normal T4 (thyroxine).
Diagnosis
Contributing factors may be:
• endemic iodine deficiency or iodine excess • iatrogenic secondary to thyroid surgery • radioablation or radiation to the neck • medications, such as amiodarone or lithium • congenital absence of the thyroid gland • autoimmune disorders such as Hashimoto's thyroiditis
During your review of the system, ask the patient if they are experiencing:
• lethargy • course dry skin • fatigue • hair loss • cold intolerance • menstrual irregularities (adult female population) • constipation • Cognitive/ memory changes.
During physical exam, pay particular attention to the following: General: Weight gain and bradycardia Dull expression, swollen face, periorbital edema, decreased auditory HEENT: acuity, swollen tongue, hoarseness, enlarged thyroid gland (goiter), glandular atrophy and thyroid nodules. Bradycardia, LV hypertrophy, mild hypotension or diastolic CV: hypertension, decreased heart sounds. Respiratory: Bradypnea, diminished vital capacity and total lung capacity, dyspnea Abdominal: Hypoactive bowel sounds and abdominal bloating MSK: Swollen hands, swollen feet and leg edema Dementia, paranoid ideation, slow delayed reflexes and cerebellar NEURO: ataxia PSYCHE: Depression Dry skin, pale, course dry hair, brittle nails, hair loss, and temporal SKIN: thinning of eyebrows
Differential diagnosis for hypothyroidism includes:
• Depression • Obesity • Dementia • Coronary heart disease • Congestive heart failure • Kidney failure • Cirrhosis • Nephrotic syndrome • Chronic kidney disease
Diagnostic tests to order if you suspect hypothyroidism include:
• Thyroid panel (TSH, Free T4)- o Overt hypothyroidism will demonstrate an increase in TSH and a decrease in T3 and T4 levels o Subclinical hypothyroidism may show an increased but normal level of TSH with normal levels of free T4 • CBC for anemia • Electrolytes (hyponatremia) • Glucose (hypoglycemia) • BUN/creatinine • Albumen • Lipid panel Treatment
• Daily thyroid replacement. • Thyroid replacement doses are based on laboratory results. • Older adults may metabolize T4 more slowly than younger persons. Dosage adjustment may be necessary. • When prescribing a daily thyroid replacement remember a few points: o Prescribe with caution in older adults with cardiovascular co-morbidities. o Educate patients about how to take medications – same time each day, on an empty stomach, full glass of water. o Avoid concomitant use with aluminum hydroxide antacids as it prevents absorption of the thyroid replacement. o Avoid calcium supplements within 4 hours of thyroid replacement due to decrease in absorption of thyroid replacement. o Thyroid replacement may interfere with the mechanism of action of the following medications: tricyclic antidepressants, aminophylline, theophylline, warfarin, phenytoin, carbamazepine, beta blockers, digoxin and testosterone (DeLong, 2012).
References
Agency for Healthcare Research and Quality (2010). Thyroid function tests: Diagnoses and monitoring of thyroid function disorders in adults.
Carroll, P. (2009). Hypothyroid disease. Evidence –based nursing monographs.
DeLong, M.F. (2012). Thyroid dysfunction. CME Resource.
The American Thyroid Association. (2012). Thyroid Disease in the Older Patient.