Endocrine Abstracts

The maturation of hypothalamo-pituitary-gonadal (HPG) axis causes the onset of puberty, which stimulates the development of secondary sex characteristics and changes in the size and composition of the body. Furthermore, the size of the thyroid gland increases and its function also changes as an adaptation to the requirements of the transformation of child to an adult. It has also been reported that the thyroid hormones including thyroxin (T4) and triiodothyronine (T3) have a facilitative action on the reactivation of the release of GnRH in pulsatile pattern at the time of puberty. In humans, it has been suggested that thyroid hormones affect reproductive functions and fertilizing ability since T3 has been demonstrated to have an essential function in testicular development by controlling the differentiation and proliferation of Leydig and Sertoli cells by binding to Sertoli cells during the development of testes. It has been reported that the proper functioning hypothalamo-pituitary-thyroid (HPT) axis is essential for proper reproductive development in human. The secretion of thyroid hormones is altered under different physiological and pathological conditions including puberty and stress. The current investigation was planned to systematically examine possible associations between plasma concentrations of T3 and FSH, LH, T and inhibin B at different ages and developmental stages in boys between 1 to 20 years of age (27 boys/age group). The concentrations of T3, FSH, LH, T and inhibin B were determined using specific ELISA systems. The data were analyzed using Student’s t test, ANOVA and Pearson correlation r. The concentrations of T3 and FSH were positively correlated at 1st-3rd, 7th-12th, 14th, 18th and 19th year of age and at infancy, early, mid and late puberty. Moreover, the concentrations of T3 and LH were positively correlated at 1st, 6th, 9th to 15th, 17th and 19th year of age and at all developmental stages including infancy, pre-puberty, early, mid and late puberty. Similarly, T3 and T concentrations were positively correlated at 1st, 3rd, 6th, 8th to 15th, 17th, 19th and 20th year of age and at all developmental stages. Furthermore, T3 and inhibin B levels were positively correlated at 1st, 3rd-6th, 10th-14th, 18th and 20th year of age and at infancy, pre-puberty, early and mid-puberty. In conclusion, T3 and LH and T levels were found to be positively correlated at all developmental stages from infancy to late puberty, whereas T3 and FSH and inhibin B levels were positively correlated at infancy, early puberty and mid-puberty.