Serum thyroid hormone levels in healthy children from birth to adulthood and in short children born small for gestational age.
BACKGROUND
Age-appropriate reference ranges for thyroid hormones are required for detecting pediatric thyroid dysfunction. Data on thyroid hormones and peripheral thyroid metabolism in short children born small for gestational age (SGA) before and during GH treatment are lacking.


OBJECTIVE
Our objectives were to obtain pediatric thyroid hormone reference ranges; to investigate thyroid hormones in short SGA children before puberty, during puberty, and during postponement of puberty by GnRH analog; and to evaluate thyroid hormones during GH treatment.


METHODS
In 512 healthy children (225 females; 0-18 yr), free T(4) (FT(4)), TSH, total T(4), T(3), rT(3), and T(4)-binding globulin were determined. Reference ranges were calculated using the linearity, median, and skewness method. In 125 short SGA children (62 females; mean age 11.3 yr), thyroid hormones were analyzed before and after 2 yr of GH treatment and additional GnRH analog.


RESULTS
Thyroid references showed wide ranges postnatally and age-specific patterns thereafter, similar in boys and girls. Untreated short SGA children had similar FT(4) and T(4) levels as the reference population but significantly higher T(3), rT(3), and T(4)-binding globulin levels. During puberty and during GH treatment, FT(4) and rT(3) significantly decreased, whereas T(3) significantly increased.


CONCLUSIONS
Age-specific thyroid reference ranges are presented. Puberty and GH treatment both induce changes in peripheral thyroid metabolism, resulting in more biologically active T(3) at the expense of less inactive rT(3), possibly mediated by IGF-I. GH treatment induces altered peripheral thyroid metabolism but does not result in thyroid dysfunction.
Dutch Growth Research Foundation, P.O. Box 23068, 3001 KB Rotterdam, The Netherlands. a.lem@kindengroei.nl
Annemieke J
AJ
Lem
Yolanda B
YB
de Rijke
Hans
H
van Toor
Maria A J
MA
de Ridder
Theo J
TJ
Visser
Anita C S
AC
Hokken-Koelega
D000293:Adolescent; D000375:Aging / Q000502:physiology; D001827:Body Height / Q000502:physiology*; D002648:Child; D002675:Child, Preschool; D005260:Female; D019382:Human Growth Hormone / Q000627:therapeutic use; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D007236:Infant, Small for Gestational Age / Q000502:physiology*; D008297:Male; D011627:Puberty / Q000502:physiology; D011628:Puberty, Delayed / Q000097:blood / Q000209:etiology; D011994:Recombinant Proteins / Q000627:therapeutic use; D012015:Reference Standards; D012016:Reference Values; D013960:Thyroid Function Tests; D013963:Thyroid Hormones / Q000097:blood*; D013974:Thyroxine / Q000097:blood; D056825:Thyroxine-Binding Globulin / Q000032:analysis; D014284:Triiodothyronine / Q000097:blood; D014285:Triiodothyronine, Reverse / Q000097:blood
D011994:Recombinant Proteins; D013963:Thyroid Hormones; D056825:Thyroxine-Binding Globulin; D014284:Triiodothyronine; D019382:Human Growth Hormone; D014285:Triiodothyronine, Reverse; D013974:Thyroxine