HPG-axis hormones during puberty: a study on the association with hypothalamic and pituitary volumes.

OBJECTIVE: During puberty, the hypothalamus-pituitary-gonadal (HPG) axis is activated, leading to increases in luteinizing hormone (LH), follicle stimulating hormone (FSH) and sex steroids (testosterone and estradiol) levels. We aimed to study the association between hypothalamic and pituitary volumes and development of pubertal hormones in healthy pubertal children.
METHOD: Hormone levels of LH, FSH, estradiol (measured in urine) and testosterone (measured in saliva) were assessed in 85 healthy children (39 boys, 46 girls) between 10 and 15 years of age. Hypothalamic and pituitary gland volumes were segmented on high resolution structural MRI scans. Since sex hormone production is regulated in a sex-specific manner, associations between hormones, hypothalamus and pituitary were analyzed in boys and girls separately.
RESULTS: LH, estradiol and testosterone levels all increased with age in both sexes, whereas FSH level did not. Pituitary volume also increased with age and explained 12%, 10% and 8% of the variance in female estradiol, testosterone and LH levels respectively. Corrected for age, pituitary volume explained 17% of FSH level in girls (not boys). Hypothalamic volume did not change with age and did not significantly explain variance in any hormonal level. DISCUSSION: Our study suggests that a larger pituitary volume is related to higher FSH production, but this association seems independent of pubertal development. The positive association between estradiol, LH and testosterone and pituitary volume is related to age-related pubertal development. With respect to the hypothalamus, we did not find convincing evidence for a larger structure to be involved in elevated hormonal production.