Exaggerated TSH responses to TRH in patients with goiter and 'normal' basal TSH levels.
OBJECTIVE
The availability of sensitive thyrotropin (TSH) assays decreased the diagnostic value of thyrotropin-releasing hormone stimulation tests (TRH-ST) in subclinical hypothyroidism. In this study we aimed to evaluate the relation between basal and stimulated serum TSH levels on TRH-ST and to determine the prevalence of patients with normal basal serum TSH and exaggerated TSH responses.


METHODS
179 patients (117 girls, 123 pubertal) with a median age of 12 (2.7-21.4) years who presented with goiter were enrolled and evaluated for their pubertal stage, height, thyroid autoimmunity, ultrasonography, thyroid function, and TRH-ST. Serum TSH concentrations were determined by sensitive assays. At TRH-ST, a peak serum TSH level >25 mIU/l was considered as an exaggerated response.


RESULTS
30 (17%) patients had an exaggerated TSH response. In patients with serum TSH levels between 2 and 4.68 mIU/l (upper half the normal range), an exaggerated TSH response was observed in 19.5%. A positive correlation between basal and TRH-stimulated TSH levels was determined (r = 0.536, p < 0.01). In patients with an exaggerated TSH response, 23 had normal (discordant) and 7 had high basal TSH levels (concordant). The mean basal serum TSH level was lower in the discordant group compared to the concordant group (p < 0.01).


CONCLUSIONS
Basal serum TSH levels might not be sufficient for diagnosing subclinical hypothyroidism. Stimulated TSH levels on TRH-ST are valuable, especially when serum TSH concentrations are in the upper half of the normal range.
Evliyaoğlu
Olcay
O
Pediatric Endocrinology Department, School of Medicine, Ankara University, Oran Sitesi Oran, Ankara, Turkey. olcayevliyaoglu@hotmail.com
Berberoğlu
Merih
M
Ocal
Gönül
G
Adiyaman
Pelin
P
Aycan
Zehra
Z
D000293:Adolescent; D000328:Adult; D002648:Child; D002675:Child, Preschool; D005260:Female; D006042:Goiter / Q000175:diagnosis / Q000503:physiopathology*; D006801:Humans; D007037:Hypothyroidism / Q000175:diagnosis; D013972:Thyrotropin / Q000097:blood*; D013973:Thyrotropin-Releasing Hormone
D013973:Thyrotropin-Releasing Hormone; D013972:Thyrotropin