ESPE Yearbook of Paediatric Endocrinology

Brief Summary: This cohort study examined the longitudinal growth trajectory of children with congenital hypothyroidism (CH) during the first 3 years of life. It involved 1474 children in Isfahan Province, Iran, and analyzed data from 2002-2022 since the initiation of CH screening (May 2002).

Overall, 38.8% of children with CH were born of consanguineous marriages and 61.6% were delivered by cesarian section, one of the highest rates in the world^1,2. Delays were noted in weight gain (37%), linear growth (36.6%), and head growth (25.7%). The sex distribution showed a consistently higher proportion of male infants. This contrasts with the usual reported higher prevalence in females compared to males (1.5 to 2.0 to 1)⁴. Factors influencing growth patterns included gender (length/height z-score), treatment initiation age (all growth parameters), delivery method (length/height z-score), parental consanguinity (all growth parameters), history of familial hypothyroidism (all growth parameters), and thyroid-stimulating hormone (TSH) levels at 3-7 days (all growth parameters).

Three distinct trajectories of weight and head circumference z-scores were identified. An ‘’optimal growth” group (62.5% of infants) showed lower average TSH levels during the period of study. Four trajectories were noted for linear growth; the “optimal growth” group (63.4% of infants) had lower TSH on screening (mean 10.3 mIU/L) but more likely had delayed treatment initiation, suggesting that some of them had transient or less severe CH, e.g. as in pseudohypoparathyroidism. Two other groups showed declining length/height z-scores: those with the steepest decline in growth velocity (11% of infants) had the highest rate of consanguinity and highest TSH on screening (mean 50.1 mIU/L) despite timely initiation of treatment.

Barriers to achieving proper growth in children with CH include delayed diagnosis, insufficient dosage of thyroid hormone and non-adherence, and also wider factors such as poor nutrition, chronic illness, exposure to toxins, socioeconomic factors and genetic background. National studies such as this one provide valuable insights into the local prevalence (several fold higher in some areas of Iran than other countries^3,4) and specific challenges faced in managing CH, including issues related to screening and follow-up care⁵.

While many previous cross sectional and longitudinal studies have shown that the growth of children with CH is comparable to that of healthy children, a value of the current approach to identify differing growth trajectories could unmask specific groups needing more attention.

References: 1. Betran A, Ye J, Moller A-B, Souza J, Zhang J. Trends and projections of caesarean section rates: global and regional estimates. BMJ Global Health, 2021;6:e005671. doi:10.1136/bmjgh-2021-005671.2. Azami-Aghdash, S, Ghojazadeh M, Delhdilani N, Mohammadi M, Asa Amin Abad R. Iranian J Publ Health, 2014;43:545-555. PMID: 26060756 PMCID: PMC4449402.3. Danner E, Niuro L, Huopio H, Niinikoski H, Viikari L, Kero J, Jääskeläinen J. Incidence of primary congenital hypothyroidism over 24 years in Finland. Pediatric Research, 2023:93:649–653. doi: 10.1038/s41390-022-02118-4.4. Hemati Z, Hashemipour M, Hovsepian S, Mansourian M, Zandieh M, Ahmadian M, Dalvi M, Arefnia S, Kelishadi R. Congenital hypothyroidism in different cities of the Isfahan province: a descriptive retrospective study. J Educ Health Promot, 2019; 8:137. doi: 10.4103/jehp.jehp_219_18.5. Yarahmadi S, Shahin B, Parvizi H, Motaghi R, Rahmani K. Physical development at school entry in children with congenital hypothyroidism diagnosed by the national program of newborn screening in Iran. Int J Endocrinol Metab. 2023; 21:e131081. doi: 10.5812/ijem-131081.