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NeoReviews Vol.7 No.2 2006 e107
© 2006 American Academy of Pediatrics
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The neonate was delivered by cesarean section due to fetal distress. Meconium staining of the amniotic fluid was noted at delivery, and neonatal resuscitation was performed. The baby was not intubated for meconium suctioning. Apgar scores were 4 at 1 minute and 9 at 5 minutes. After delivery room resuscitation, the baby continued to need blow-by oxygen and was transferred to the neonatal intensive care unit (NICU) for observation.
Initial vital signs in the NICU were: weight, 2,405 g (50th percentile); length, 48 cm (25th percentile); head circumference, 31.5 cm (<3rd percentile); temperature, 98.6°F (37°C); heart rate, 148 to 150 beats/min; respiratory rate, 48 breaths/min; blood pressure, 79/53 mm Hg; and oxygen saturation on blow-by oxygen, 97% to 98%. She did well and within 3 hours was weaned to room air. At that time, she exhibited neither tachypnea nor tachycardia. No antibiotics were started. Results of her physical examination were normal, including normal female genitalia.
On the second postnatal day, a murmur was audible, and four extremity blood pressures showed: right upper, 79/53 mm Hg; right lower, 81/47 mm Hg; left upper, 86/48 mm Hg; and left lower, 74/45 mm Hg. By the third postnatal day, tachycardia is noted, with a heart rate greater than 180 beats/min and a rising blood pressure of 92/50 mm Hg. Diagnostic tests reveal the diagnosis.
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Differential Diagnosis
The differential diagnosis for the infant included respiratory distress syndrome, sepsis, congenital heart disease, late-onset group B streptococcal infection, maternal Graves disease, withdrawal from maternal opioid use, maternal narcotic use, and familial dysautonomia. The key was an increased heart rate and blood pressure that, in combination with the maternal history of thyroid disease, point to hyperthyroidism. Other clinical manifestations of neonatal hyperthyroidism include low birthweight for gestational age; preterm birth; microcephaly; frontal bossing; warm, moist skin; irritability; hyperactivity; restlessness; poor sleep; fetal hydrops; hyperphagia; hepatosplenomegaly; poor weight gain; diarrhea; and diffuse goiter.
Pathogenesis/Incidence/Natural History
Neonatal hyperthyroidism results from transplacental passage of maternal TSH-stimulating immunoglobulin G (TSI) antibodies. It may occur in women who have a history of Graves disease, whether active or treated. The incidence of neonatal Graves disease is 1 to 2 per 1,000 births from affected mothers. The cause for concern is that the infant mortality rate is 12% to 16%. The other complication is hypothyroidism caused by either placental transfer of antithyroid drugs or maternal transfer of thyrotropin-blocking antibodies (TBA). With antithyroid drugs (usually propylthiouracil because methimazole is known to cause embryologic defects), the effect is usually transient, lasting up to 10 days. The neonates may become hyperthyroid after the medication is cleared from their systems. Mothers who have active disease are maintained on the lowest possible dose, with a goal of keeping them slightly hyperthyroid. Mothers who have TBA may pass these as well as the TSI to the baby. Initially, the TBA block the hyperthyroid response, and the neonates develop hyperthyroidism between 1 to 4 weeks after birth. In all cases, the antibodies should clear from the infant circulation by 6 months of age and the hyperthyroidism resolve. If the hyperthyroidism does not resolve, other causes should be considered, such as thyrotropin-receptor activating mutations or G-protein alpha subunit-activating mutations seen in McCune-Albright syndrome.
Treatment
The treatment for neonates is driven by the clinical symptoms and laboratory values. If the patient, as in the case presented, has obvious clinical symptoms with significant TSH suppression, he or she should receive a beta blocker and an antithyroid drug. If the laboratory values show minimal changes and the patient has no obvious clinical symptoms and good growth, observation alone may be sufficient. Monthly follow-up, with more frequent laboratory evaluation, is recommended.
In this case, propranolol and propylthiouracil were administered to the infant, who responded well but soon became oversuppressed, a possibility when using antithyroid drugs. When the propylthiouracil dose was decreased, she became hyperthyroid. Because of difficulties in achieving a euthyroid state for the infant, the decision was made to suppress endogenous thyroxine production and replace with oral levothyroxine. During this time, the propranolol was discontinued as her blood pressure and pulse returned to normal limits. As she grew, her propylthiouracil doses became small enough to allow its discontinuation and that of levothyroxine without difficulty. She was followed until 1 year of age and discharged from clinic after remaining off medications for more than 6 months.
Lesson for the Clinician
Neonatal Graves disease is rare, but must be considered in infants of mothers who have a history of thyroid disease. Although the mother may not have any clinical signs or symptoms of hyperthyroidism or she is currently hypothyroid, the TSI antibodies still may be present and transferred to the neonate. All neonates in whom neonatal Graves disease is diagnosed need to be followed closely. (Chetanbabu Patel, MD, Kurt Metzl, MD, Figen Ugrasbul, MD, Children’s Mercy Hospital, Kansas City, Mo.)
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Acknowledgments |
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Footnotes |
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Drs Patel, Metzl, and Ugrasbul did not disclose any financial relationships relevant to this case.
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Suggested Reading |
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TopCase PresentationCase DiscussionSuggested Reading |
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Fisher DA. Disorders of the thyroid in the newborn and infant. In: Sperling MA, ed. Pediatric Endocrinology. Philadelphia, Pa: Saunders; 2002:161 –186
LaFranchi S. Evaluation and management of neonatal Graves disease. UptoDate. Available at www.uptodate.com. Accessed October 2005
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