Serum kisspeptin levels mainly depend on ovarian expression of Kiss1 mRNA in female rats

Urinary phthalate/DINCH metabolites associations with kisspeptin and reproductive hormones in teenagers: A cross-sectional study from the HBM4EU aligned studies

BACKGROUND

Exposure to phthalate/DINCH metabolites can induce human reproductive toxicity, however, their endocrine-disrupting mechanisms are not fully elucidated.

OBJECTIVE

To investigate the association between concentrations of phthalate/DINCH metabolites, serum kisspeptin, and reproductive hormones among European teenagers from three of the HBM4EU Aligned Studies.

METHODS

In 733 Belgian (FLEHS IV study), Slovak (PCB cohort follow-up), and Spanish (BEA study) teenagers, ten phthalate and two DINCH metabolites were measured in urine by high-performance liquid chromatography-tandem mass spectrometry. Serum kisspeptin (kiss54) protein, follicle-stimulating hormone (FSH), total testosterone (TT), estradiol (E2), and sex hormone-binding globulin (SHBG) levels were measured by immunosorbent assays. Free Androgen Index (FAI) was calculated as a proxy of free testosterone. Adjusted sex-stratified linear regression models for individual studies, mixed effect models (LME) accounting for random effects for pooled studies, and g-computation and Bayesian kernel machine regression (BKMR) models for the phthalate/DINCH mixture were performed.

RESULTS

The LME suggested that each IQR increase in ln-transformed levels of several phthalates was associated with lower kisspeptin [MnBP: %change (95%CI): -2.8 (-4.2;-0.4); MEHP: -1.4 (-3.4,0.2)] and higher FSH [∑DINP: 11.8 (-0.6;25.1)] levels in females from pooled studies. G-computation showed that the phthalates/DINCH mixture was associated with lower kisspeptin [-4.28 (-8.07;-0.34)] and higher FSH [22.13 (0.5;48.4)] also in females; BKMR showed similar although non-significant pattern. In males, higher phthalates metabolites [MEHP: -12.22 (-21.09;-1.18); oxo-MEHP: -12.73 (-22.34;-1.93)] were associated with lower TT and FAI, although higher DINCH [OH-MINCH: 16.31 (6.23;27.35), cx-MINCH: 16.80 (7.03;27.46), ∑DINCH: 17.37 (7.26;29.74)] were associated with higher TT levels. No mixture associations were found in males.

CONCLUSION

We observed sex-specific associations between urinary concentrations of phthalate/DINCH metabolites and the panel of selected effect biomarkers (kisspeptin and reproductive hormones). This suggests that exposure to phthalates would be associated with changes in kisspeptin levels, which would affect the HPG axis and thus influence reproductive health. However, further research is needed, particularly for phthalate replacements such as DINCH.

Kisspeptin and DLK1 levels for monitoring treatment of girls with central precocious puberty

BACKGROUND

Kisspeptin and delta-like 1 homolog (DLK1) are neuropeptides that reportedly play an important role in pubertal timing by activating and inhibiting the hypothalamic-pituitary-gonadal axis, respectively. Consequently, serum kisspeptin and DLK1 levels may be novel biomarkers for differentiating between central precocious puberty (CPP) and premature thelarche (PT) in girls and used to monitor CPP treatment.

PURPOSE

To compare baseline serum kisspeptin and DLK1 levels in girls with CPP at diagnosis and after treatment to age-matched girls with PT.

METHODS

This prospective longitudinal study included girls with precocious puberty and girls with PT who experienced breast development before 8 years of age and peak luteinizing hormone levels of ≥6 versus <6 IU/L after a gonadotropin-releasing hormone (GnRH) stimulation test. Serum kisspeptin and DLK1 levels were determined in both groups at baseline and after 6 months of GnRH analog treatment in the CPP group and analyzed by enzyme-linked immunosorbent assay.

RESULTS

The study divided a total of 48 girls into CPP (n=24; mean age, 7.7±0.7 years) and PT (n=24; mean age, 7.4±0.8 years) groups. The baseline median serum kisspeptin levels were 50.5 pg/mL (range, 38.2-77 pg/mL) and 49.5 pg/mL (range, 39.7-67.6 pg/mL), respectively (P=0.89), while the baseline median serum DLK1 levels were 6.5 ng/mL (range, 5.9-7.5 ng/mL) and 6 ng/mL (4.4-14.4 ng/mL), respectively (P=0.68). After 6 months of GnRH analog treatment in the CPP group, the median serum kisspeptin level was lower (46.4 ng/mL; range, 37.1-60 ng/mL) than that at baseline (P=0.002), while the median serum DLK1 level was higher (7 ng/mL; range, 6.7-8.9) than that at baseline (P=0.002).

CONCLUSION

Our findings suggest that baseline serum kisspeptin and DLK1 levels are not reliable biomarkers for differentiating between CPP and PT. However, significant changes in serum kisspeptin and DLK1 levels may be used to monitor CPP treatment.

Central precocious puberty: a review of diagnosis, treatment, and outcomes

Central precocious puberty (CPP) refers to early activation of the hypothalamic-pituitary-gonadal (HPG) axis and is manifested by breast development in girls or testicular enlargement in boys before the normal physiological age ranges. CPP can be precipitated by intracranial pathology, exposure to high levels of sex steroids, or environmental risk factors, but most cases are idiopathic. Monogenic causes have also been identified. In this Review, we summarise pathophysiology, risk factors, diagnosis, and management of CPP. Concern for CPP should prompt referral to paediatric endocrinology where diagnosis is confirmed by clinical, biochemical, radiological, and genetic testing. CPP is treated with a gonadotropin-releasing hormone analogue, the primary aims of which are to increase adult height and postpone development of secondary sexual characteristics to an age that is more commensurate with peers. Although long-term outcomes of treatment with gonadotropin-releasing hormone analogues are reassuring, additional research on the psychological effect of CPP is needed.