Elevated serum TSH concentrations are associated with higher BMI Z-scores in southern Iranian children and adolescents

Abstract

Background Subclinical hypothyroidism is defined as elevated TSH levels while T4 or FT4 levels are normal. Elevated TSH levels are linked with obesity in adults. In a recent meta-analysis in Iran, 6.1% of children below 18 had obesity. Due to the low number of studies on the subject in children we, designed the study to assess the relation between BMI Z-score and TSH levels in children and adolescence. Method This cross-sectional study was performed in a pediatric endocrinology clinic in Shiraz. Children aged between 2 to 18 years that came to the clinic for routine growth assessment follow up from January till April 2018 were considered. 850 children including 365 boys and 485 girls were included. Results Prevalence of subclinical hypothyroidism is increased in higher BMI groups. 9.9, 13.8, 17.2 and 20.5% of underweight, healthy weight, overweight and obese had subclinical hypothyroidism respectively. Obese and overweight participants had higher odds of subclinical hypothyroidism than those who were not (OR:1.649, P = 0.010, CI95% 1.126–2.413). On the other hand, Subclinical hypothyroid participants had higher odds of overweight or obesity than those who were euthyroid (OR:1.650, P = 0.010, CI95% 1.128–2.413). When TSH is set as a dependent value, TSH level is increased (β = 0.126, r = 0.125, P = 0.001) with an increase in BMI Z-score. When BMI Z-score is set as a dependent value, BMI Z-score is increased (β = 0.113, r = 0.243, P = 0.001) with an increase in TSH level. Conclusion BMI Z-score and elevated TSH levels are positively correlated however studies should be performed on establishing the causality.

Longitudinal Associations Between TPO Gene Variants and TPOAb Seroconversion in a Population Based Study: Tehran Thyroid Study (TTS)

“…It is suggested that weight gain increases the incidence of thyroid autoimmunity. The association between obesity and the increased prevalence of autoimmune diseases, including AITDs, has been reported in several previous studies (23)(24)(25)(26)(27). The observations of this study were in line with previous studies.…”

Función tiroidea en escolares con obesidad

“…Las posibles causas de los casos de hipotiroidismo subclínico con TSH elevada y T3 y T4 libres en concentraciones normales, incluyen disfunción neuroendocrina, resistencia a las hormonas tiroideas, modificación de la producción de TSH mediada por la leptina, y mutaciones del receptor de TSH (23). Nuestros resultados respecto al hipotiroidismo subclínico, concuerdan con estudios internacionales, donde se estima una prevalencia en niños obesos entre 7,5 y 23% (6,9,(24)(25)(26). La obesidad tiene influencia sobre la actividad del eje hipotálamo -hipófisis -tiroides, lo cual se evidencia mediante una elevación de la TSH en ausencia de déficit de Iodo y de alguna enfermedad tiroidea autoinmune (3,6).…”

“…De los obesos con hipotiroidismo, un alto porcentaje presentó T3 libre baja, o T4 libre baja, con TSH normales, es decir no hubo una respuesta compensadora de la glándula tiroides para normalizar los valores de las hormonas periféricas, por falta de estímulo hipotálamo o hipofisiario (13). Estos resultados difieren de estudios internacionales, quienes hallaron mayormente hipotiroidismo del tipo subclínico (6,9,(24)(25)(26). El hipotiroidismo primario constituye la enfer-medad endocrinológica más frecuente de la infancia, las formas hipotálamo-hipofisarias son poco frecuentes y generalmente se asocian a otras deficiencias hormonales, que son las que destacan y conducen al diagnóstico.…”

“…A semejanza con Thiagarajan y col (31), no se encontró correlación de las pruebas tiroideas con las variables antropométricas en estudio. Estos hallazgos difieren a lo reportado por la literatura (9,24,26,32), donde señalan que los niveles séricos de TSH aumentan en paralelo con el IMC, la CC y la adiposidad, existiendo una correlación negativa entre los valores de T4 libre y el IMC. Estas diferencias pudieran deberse, a que por las escasas publicaciones de disfunción tiroidea en la edad escolar, se realizaron comparaciones con estudios que incluyeron preescolares y adolescentes; es conocido que la composición corporal en relación a masa magra y adiposidad varía según el grupo etario (33).…”

Transient Hyperthyrotropinemia in Outpatient Children with Acute Infections of the Respiratory System

“…In children, the level of TSH appears to be a stable and solid diagnostic parameter, however, its variability in laboratory tests has been observed [11]. On the other hand, there are some conditions in which the transitionally elevated TSH concentration is observed, with obesity being one of the welldocumented examples [12]. Studies concerning the influence of other transient conditions (e.g., inflammations) on TSH secretion are divergent [13,14].…”