The within-pair resemblance in serum levels of androgens, sex-hormone binding globulin and cortisol in female obese identical twins - effect of negative energy balance induced by very low-calorie diet.

The first aim of the present study was to evaluate the changes in serum levels of cortisol, testosterone, dehydroepiandrosterone (DHEA), dehydroepiandrosterone sulphate (DHEA-S) and sex hormone-binding globulin (SHBG) in response to weight loss induced by one month of treatment with a very low-calorie diet (VLCD) in twelve pairs of female obese monozygotic twins. The second aim of the study was to investigate any within-pair resemblance in serum levels of steroids and SHBG before and after a negative balance protocol, as well as the resemblance in changes in response to therapeutic weight loss. VLCD-induced weight loss of 8.7+2.9 kg was associated with significant increases in serum testosterone (p<0.05) and SHBG (p<0.001) levels, whereas no significant changes in serum levels of cortisol, DHEA and DHEA-S were observed. Significant within-pair resemblances for both pre-treatment and post-treatment concentrations were revealed for DHEA-S (pre-treatment ICC = 0.795, p < 0.01, post-treatment ICC = 0.712, p < 0.01) and for testosterone (pre-treatment ICC = 0.594, p <0.05, post-treatment ICC = 0.735, p < 0.01). The baseline within-twin-pair resemblance in serum cortisol level at 7 a.m. (ICC=0.747, p < 0.05) was lost with VLCD treatment, while its concentration at 9 p.m. developed a within-pair similarity with weight loss (ICC = 0.824, p < 0.001). Similarly, VLCD treatment led to a significant within-pair resemblance in post-treatment level of DHEA (ICC = 0.755, p < 0.01), while no within-twin-pair resemblance was shown for either pre-treatment or post-treatment SHBG levels. None of the hormones measured exhibited any within-pair resemblance in response to VLCD-induced energy deficit, except for serum cortisol levels. A significant within-twin-pair resemblance in the changes in serum cortisol levels at 7 a. m. (ICC = 0.789, F = 8.5, p < 0.001), at 1 p.m. (ICC = 0.660, F = 4.9, p <0.01) and at 9 p.m. (ICC = 0.795, F = 8.8, p <0.001) were demonstrated even after adjustment for fat mass loss. An absence of any within-pair similarity was observed in both pretreatment and post-treatment levels of SHBG, while a significant within-pair resemblance in SHBG response to VLCD treatment (ICC = 0.658, p < 0.05) was recorded. We conclude that the significant within-twin-pair resemblance demonstrated for androgens and cortisol might suggest an important role for genetic factors in the regulation of their serum levels. Our results also suggest that the mechanisms controlling baseline levels of cortisol and SHBG differ from those influencing their responses to energy deficit induced by VLCD.