ECE2014 Poster Presentations Thyroid (non-cancer) (125 abstracts)
An increase in the circulating concentrations of triiodothyronine appears to be a function of the peripheral conversion of tetraiodothyronine by deiodinases instead of increased stimulation by thyroid stimulating hormone at puberty in normal healthy boys
SSR Rizvi 1, , Hafsa Asif 1 , Sadia Saqib 1 , Nadia Perveen 1 , Ghazala Shaheen 1 , AA Naseem 1 , Faheem Tahir 2 & Mazhar Qayyum 1
1Department of Zoology, PMAS Arid Agriculture University, Rawalpindi, Pakistan; 2Department of Reproductive Physiology, National Institute of Health, Islamabad, Pakistan; 3Pakistan Science Foundation, Islamabad, Pakistan.
Thyroid stimulating hormone (TSH) causes synthesis of 90% of pro-hormone tetraiodothyronine (T4) and 10% of active triiodothyronine (T3) from thyroid gland. T3 regulates energy metabolism, thermogenesis, body temperature and normal brain development. T3 is produced from deiodination of T4 and circulating levels of T3 are regulated by deiodinases in response to body’s needs. The peripheral conversion of T4 to T3 by determining age and pubertal stage dependent changes in circulating concentrations of TSH, T4 and T3 in boys (n=671) of 1 to 20 years was investigated. Blood samples were collected and concentrations of TSH, T4 and T3 were determined. Data were analyzed using Student’s t test, anova and Pearson correlation. The concentrations of TSH increased to a peak at 5th year, remained low till 9th year, exhibited a 2nd peak at 12th year and later showed peaks at alternate years. The concentrations of TSH were higher at infancy, increased at prepuberty, declined at early puberty and showed a peak at mid puberty. The levels of T4 were higher during 1st nine years, slightly increased during 14th and 15th years and decreased to lower levels by 20th year. The concentrations of T3 were low during first eight years, increased progressively reaching peak levels at 17th year and maintained by 20th year. The peripheral conversion of T4 to T3 was low as high concentrations of T4 and low of T3 were observed during first decade. The plasma concentrations of T4 kept on decreasing and those of T3 kept on increasing during second decade. The concentrations of T4 gradually declined from infancy to late puberty/adolescent, whereas those of T3 progressively increase from prepuberty to late puberty/adolescent. In conclusion, the present study indicates that the activity of diodenases increases at puberty causing greater conversion of T4 to T3 in response to increased metabolic demand.
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Endocrine Abstracts
ISSN 1470-3947 (print) | ISSN 1479-6848 (online)
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