A 15-DAY-OLD premature infant (gestational age, 32 weeks) was
noted to have a prominent midline neck mass (Figure). Thyroid
function studies revealed the following values: thyroxine, 12.87
nmol/L (1 μg/dL) (normal range, 58-154 nmol/L [4.5-12 μg/dL]);
triiodothyronine, 1.2 nmol/L (80 ng/dL) (normal range, 1.3-3.1
nmol/L [87-200 ng/dL]); and thyroid-stimulating hormone, 95 mU/L
(normal range, 1.7-9.1 mU/L). There was no history of maternal
ingestion of goitrogenic medications or excessive exposure to
iodine-containing substances. Thyroxine replacement (10 μg/kg
per day) was begun; the goiter disappeared within 2 weeks, and
the abnormal thyroid function test results reverted to normal by
the time the patient was 4 months old. Denouement and Discussion
Transient Primary Hypothyroidism Transient primary
hypothyroidism (TPH) is a temporary hypofunction of the thyroid
gland, more common in some parts of the world than in others.
The abnormal thyroid function persists for a variable time after
birth and is often rel