The left thyroid lobe is absent in thyroid
hemiagenesis
(July 2003)
The background of the study. Absence
(agenesis) of one lobe of the thyroid gland is a rare anomaly that
is usually detected by thyroid imaging in patients thought to have
a thyroid disorder. In this study, the frequency of thyroid hemiagenesis
was determined in a population-based group of healthy children.
How the study was done. Between
1999 and 2001, 24,032 children (12,280 girls, 11,752 boys) aged
11 to 14 years living in Sicily underwent thyroid ultrasonography
as part of a study of iodine nutrition. The length, depth, and width
of both thyroid lobes were measured, and the volume was calculated
as the volume of an ellipsoid (  /6
x length x depth x width). Thyroid hemiagenesis was defined as complete
absence or marked hypoplasia (volume <10 percent of that of normal)
of a thyroid lobe. Serum free thyroxine (T4), free triiodothyronine
(T3), and thyrotropin (TSH) were measured in most of the affected
children and in 18 age- and sex-matched normal children.
The results of the study. Twelve
of the 24,032 children (0.05 percent) had thyroid hemiagenesis (seven
boys [1:1678; 0.06 percent], five girls [1:2456; 0.04 percent]).
Eleven children had complete absence of the left thyroid lobe, and
one had severe hypoplasia of the left lobe. The volume of the remaining
lobe in these 12 children was similar to the average total thyroid
volume in normal children of the same age in 4 (33 percent), larger
in 3 (25 percent), and smaller in 5 (42 percent).
All nine children in whom thyroid function was studied had serum
TSH, free T4, and free T3 concentrations within the normal range,
although their mean serum TSH and free T3 concentrations were slightly
higher than in the 18 age-matched normal children.
The conclusions of the study. In
this large group of children, all with thyroid hemiagenesis, had
a missing left thyroid lobe, and most had some compensatory enlargement
of the remaining lobe.
The original article. Maiorana R,
Carta A, Floriddia G, Leonardi D, Buscema M, Sava L, Calaciura F,
Vigneri R. Thyroid hemiagenesis: prevalence in normal children and
effect on thyroid function. J Clin Endocrinol Metab 2003;88:1534-6.
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