Diseases of the Thyroid Flashcards
Why does Amiodarone use decrease iodine uptake in radioiodine uptake (RAIU) scans?
Amiodarone is iodine-rich but also blocks peripheral deiodination of revers T3 and T4, resulting in increased reverse T3 and T4 and a decreased T3. It can cause a patient to be hyperthyroid (due to the iodine) or hypothyroid (due to too much iodine and the peripheral deiodination). Either way, RAIU is low because the thyroid is already saturated with iodine prior to the radioiodine dose.
Compare/contrast the radioiodine uptake scan with the thyroid scan.
RAIU uses radioactive iodine to measure the percentage taken up by the thyroid. The thyroid scan uses technetium to create a picture of how the isotopes localize within the thyroid. (RAIU produces a number, thyroid scan produces a picture).
What are the expected lab findings in a patient with acquired tertiary hypothyroidism (hypothalamus-derived)?
Low TSH and low or inappropriately normal free T4
Fill in Table 15-5 for how to interpret thyroid function tests.
What should one consider if the total T4 level is outside of the normal range?
First, ensure that the thyroxine-binding globulin levels are within normal limits. If TBG is outside the normal range, total T4 will be as well, and is not clinically significant.
What is suppurative thyroiditis and where does it most commonly occur?
It is a bacterial infection of the thyroid gland and typically affects the left lobe of the thyroid.
What factors are concerning about the presence of a solitary thyroid nodule in a child?
A solitary thyroid nodule in the first 20 years of life is much more likely to be malignant than in an older person, and about 26% of thyroid nodules in children are malignant.
What prophylactic procedure is recommended for certain mutations in MEN 2A and 2B?
Certain oncogenes in MEN 2A require thyroidectomy by 5 years of age and by 6 months of age with certain oncogenes in MEN 2B.
What happens to growth in a child with acquired hypothyroidism?
Growth failure is a hallmark of the disease. In most cases growth practically ceases and patients will have a weight for age that is proportionately greater than height for age.
Which thyroid hormone should be followed in patients with primary hypothyroidism?
TSH
If a patient with a thyroid nodule undergoes a complete thyroidectomy, what is a reliable tumor marker that should be followed to monitor for recurrence?
Thyroglobulin level
What should be the first step if an infant has a positive newborn screen for congenital hypothyroidism?
Send a serum TSH and free T4 to confirm the diagnosis or to diagnose congenital TBG deficiency.
What is the recommended treatment for myxedema coma?
Thyroid hormone supplementation, stress-dose glucocorticoids (until adrenal insufficiency is ruled out), and supportive care.
What correlates with the risk of neonatal Graves’ in a baby born to a mother with Graves disease?
The maternal level of TSI (TSH receptor-stimulating antibody) determines the infant’s risk for developing neonatal Graves disease as well as its’ severity. Maternal thyroid function tests have no predictive value for the infant.
What characterizes APS (autoimmune polyglandular syndrome) Type 2?
Autoimmune thyroiditis accompanied by diabetes mellitus and adrenal cortical insufficiency. It usually presents in young adults.
What is the most likely cause of elevated TSH in a patient on levothyroxine?
This value would be indicative of noncompliance until proven otherwise.
What symptoms should patients be instructed to go to the ED for if they are undergoing medical management for Graves disease? Why?
If patients develop sore throat and mouth ulcers while taking either methimazole or PTU for treatment of Graves disease they should present to the ED for evaluation of possible agranulocytosis, which requires immediate attention.
What disease should be considered if a patient is found to have circulating antithyroglobulin and antithyroperoxidase antibodies?
Most patients with Hashimoto have these antibodies circulating. However, they can also be found in people with Grave’s or in normal individuals.
Which endocrine disease is characterized by autoimmune thyroiditis accompanied by diabetes mellitus and adrenal cortical insufficiency?
APS (autoimmune polyglandular syndrome)Type 2 (AKA Schmidt syndrome)
What should be used to treat infants and children with congenital hypothyroidism (drug, dose, and formulation)?
Levothyroxine; 10-15 µg/kg/day for infants, 4 µg/kg/day for older children (100 µg/m²/day at all ages); do not give liquid formulations, as there aren’t stable liquid formulations consistently available in the U.S. market.
How does Graves’ present in childhood?
Muscle weakness, anxiety, palpitations, increased appetite, weight changes (mostly weight loss, but some have weight gain), behavior problems, declining school performance, and decreased exercise tolerance. Patients frequently have cardiac signs/symptoms (cardiomegaly, widened pulse pressure, tachycardia, HTN, and gallop rhythms). 50% of patients have a thyroid bruit on exam. Tremor, excessive perspiration, and rapid tendon reflex relaxation times are also possible. Some may have goiter. In menarcheal girls, anovulatory cycles are common and they can develop oligomenorrhea or secondary amenorrhea.
What are the common presenting symptoms for neonatal Graves disease?
Irritability, flushing, tachycardia, HTN, thyroid enlargement, and exophthalmos. Cardiac arrhythmias can occur with severe disease.
What symptoms are typically associated with myxedema coma?
Diminished mental status, hypothermia, hypotension, bradycardia, hypoglycemia, and hyponatremia.
Describe the clinical and laboratory presentation of neonates with congenital hypothyroidism at birth.
Most infants are asymptomatic at birth because of transplacental passage of maternal thyroxine (T4). However, vertical transmission of T4 provides only 33% of normal levels so neonatal screening will still reveal a high TSH and a low T4.
