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Objective The hybrid close-loop system (HCL) is a rapidly emerging treatment method for type 1 diabetes (T1D), but the long-term effectiveness of the system remains unclear. This study investigates the influence of the HCL on glycemic control in children and adolescents with T1D in a real-life setting during the first year on HCL. Research design and methods This retrospective study included all the patients (n = 111) aged 3 to 16 years with T1D who initiated the HCL system between 1st of December 2018 and 1st of December 2019 in the Helsinki University Hospital. Time in range (TIR), HbA1c, mean sensor glucose (SG) value, time below range (TBR), and SG coefficient of variance (CV) were measured at 0, 1, 3, 6, and 12 month. The changes over time were analyzed with a repeated mixed model adjusted with baseline glycemic control. Results After the initiation of HCL, all measures of glycemic control, except HbA1c, improved and the effect lasted throughout the study period. Between 0 and 12 month, TIR increased (beta = -2.5 [95%CI: -3.6 - (-1.3)], p < 0.001), whereas mean SG values (beta = -0.7 [95%CI: -0.9 - (-0.4)]), TBR (beta = -2.5 [95%CI: -3.6 - (-1.3)]), and SG CV (beta = -4.5 [95%CI: -6.3 - [-2.8]) decreased significantly (p < 0.001). Importantly, the changes occurred regardless of the age of the patient. Conclusions Measurements of glycemic control, except HbA1c, improved significantly after the initiation of the HCL system and the favorable effect lasted throughout the follow-up. These results support the view that HCL is an efficacious treatment modality for children and adolescents with T1D of all ages.

Objective The role of miRNA as endocrine regulators is emerging, and microRNA mir-30b has been reported to repress Mkrn3. However, the expression of miR-30b during male puberty has not been studied. Design and methods Circulating relative miR-30b expression was assessed in sera of 26 boys with constitutional delay of growth and puberty (CDGP), treated with low-dose testosterone (T) (n =11) or aromatase inhibitor letrozole (Lz) (n =15) for 6 months and followed up to 12 months (NCT01797718). The associations between the relative expression of miR-30b and hormonal markers of puberty were evaluated. Results During the 12 months of the study, circulating miR-30b expression increased 2.4 ± 2.5 (s.d.) fold (P = 0.008) in all boys, but this change did not correlate with corresponding changes in LH, testosterone, inhibin B, FSH, or testicular volume (P = 0.25-0.96). Lz-induced activation of the hypothalamic–pituitary–gonadal (HPG) axis was associated with more variable miR-30b responses at 3 months (P < 0.05), whereas those treated with T exhibited significant changes in relative miR-30b levels in the course the study (P < 0.01–0.05). Conclusions Circulating miR-30b expression in boys with CDGP increases in the course of puberty, and appears to be related to the activity of the HPG axis.

Context Circulating levels of liver-enriched antimicrobial peptide 2 (LEAP2), a ghrelin receptor antagonist, decrease under caloric restriction and increase in obesity. The role of LEAP2 in male puberty, a phase with accelerated energy demand, is unclear. Objective This work aimed to investigate whether circulating LEAP2 levels are downregulated in boys following the onset of puberty to respond to the energy need required for growth. Methods We determined circulating LEAP2 levels in 28 boys with constitutional delay of growth and puberty (CDGP) who participated in a randomized controlled trial (NCT01797718), and were treated with letrozole (n = 15) or intramuscular low-dose testosterone (T) (n = 13) for 6 months. Blood sampling and dual-energy x-ray absorptiometry–measured body composition were performed at 0-, 6-, and 12-month visits. Results Serum LEAP2 levels decreased statistically significantly during pubertal progression (0-6 months: mean decrease –4.3 [10.3] ng/mL, P = .036 and 0-12 months: –3.9 [9.3] ng/mL, P = .033). Between 0 and 6 months, the changes in serum LEAP2 levels correlated positively with changes in percentage of body fat (rs = 0.48, P = .011), and negatively with growth velocity and estradiol levels (rs = –0.43, P = .022, rs = –0.55, P = .003, respectively). In the T group only, the changes in serum LEAP2 correlated negatively with changes in T and estradiol levels. Between 0 and 12 months, the change in LEAP2 levels correlated negatively with the change in high-density lipoprotein levels (rs = –0.44, P = .022) and positively with the change in insulin (rs = 0.50, P = .009) and HOMA-IR (rs = 0.51, P = .007) levels. Conclusion Circulating LEAP2 levels decreased after induction of puberty reciprocally with increased growth rate and energy demand, reflecting the metabolic state of the adolescent. Further, the results suggest that estradiol levels may have a permissive role in downregulating circulating LEAP2 levels.

Sex steroids play an important role in regulating postnatal growth. The interplay between androgens and estrogens is mediated through the activity of aromatase enzyme, which catalyzes the synthesis of estrogens from androgens. Aromatase inhibitors (AIs) are compounds that block the function of the enzyme resulting in depletion of estrogens. In men, estrogens induce pubertal growth spurt and closure of epiphyseal plates, and thus contribute to the attainment of adult height. After loosening of the central restrain of puberty, estrogens in the large part mediate the negative feedback to the hypothalamus and pituitary, and thus control the activity of the hypothalamic–pituitary–gonadal axis. Consequently, AIs have been used in adolescent boys to treat idiopathic short stature and delayed puberty. In this article, we review the published data on the impact of potent 3rd generation AIs on gonadal function and growth in pubertal boys.

This case of congenital tuberculosis (TB) emphasizes that TB should be suspected in newborns whose parents are from areas with high incidence of TB or who present with symptoms of an infection unresponsive to wide‐spectrum antibiotics.

OBJECTIVE The influence of androgens and oestrogens on growth is complex, and understanding their relative roles is important for optimising the treatment of children with various disorders of growth and puberty. DESIGN We examined the proportional roles of androgens and oestrogens in the regulation of pubertal growth in boys with constitutional delay of growth and puberty (CDGP). The study compared 6-month low-dose intramuscular testosterone treatment (1 mg/kg/month; n = 14) with per oral letrozole treatment (2.5 mg/day; n = 14) which inhibits conversion of androgens to oestrogen. PATIENTS Boys with CDGP were recruited to a randomized, controlled, open-label trial between 2013 and 2017 (NCT01797718). MEASUREMENTS The patients were evaluated at 0-, 3- and 6-month visits, and morning blood samples were drawn. Linear regression models were used for data analyses. RESULTS In the testosterone group (T-group), serum testosterone concentration correlated with serum oestradiol concentration at the beginning of the study and at 3 months, whereas in the letrozole group (Lz-group) these sex steroids correlated only at baseline. Association between serum testosterone level and growth velocity differed between the T and Lz groups, as each nmol/L increase in serum testosterone increased growth velocity 2.7 times more in the former group. Serum testosterone was the best predictor of growth velocity in both treatment groups. In the Lz-group, adding serum oestradiol to the model significantly improved the growth estimate. Only the boys with serum oestradiol above 10 pmol/L had a growth velocity above 8 cm/year. CONCLUSIONS During puberty promoting treatment with testosterone or aromatase inhibitor letrozole, growth response is tightly correlated with serum testosterone level. A threshold level of oestrogen appears to be needed for an optimal growth rate that corresponds to normal male peak height velocity of puberty. Serum testosterone 1 week after the injection and serum testosterone and oestradiol 3 months after the onset of aromatase inhibitor treatment can be used as biomarkers for treatment response in terms of growth.

The treatment of constitutional delay of growth and puberty (CDGP) is an underinvestigated area in adolescent medicine. We tested the hypothesis that peroral aromatase inhibition with letrozole is more efficacious than intramuscular injection of low-dose testosterone in inducing puberty in boys with CDGP.We did a randomised, controlled, open-label trial at four paediatric centres in Finland. Boys aged at least 14 years with CDGP who wanted medical intervention and exhibited the first signs of puberty were randomly assigned in blocks of ten to receive either six intramuscular injections of low-dose testosterone (about 1 mg/kg bodyweight) every 4 weeks for 6 months or peroral letrozole 2·5 mg once daily for 6 months. All boys were followed up for 6 months after the end of treatment. The primary outcomes were changes in testicular volume and hormonal markers of puberty at 6 months after treatment initiation, which were assessed in all participants who received the assigned treatment. All patients were included in the safety analysis. This study is registered with ClinicalTrials.gov, number NCT01797718.Between Aug 1, 2013, and Jan 30, 2017, 30 boys were randomly assigned to receive testosterone (n=15) or letrozole (n=15). One boy in the testosterone group was excluded from the primary analyses because of a protocol deviation. During treatment, boys in the letrozole group had higher serum concentrations of luteinising hormone, follicle-stimulating hormone, testosterone, and inhibin B than did boys in the testosterone group. Testicular growth from baseline to 6 months was greater in the letrozole group than in the testosterone group (7·2 mL [95% CI 5·2-9·3] vs 2·2 mL [1·4-2·9]; between-group difference per month 0·9 mL [95% CI 0·6-1·2], p0·0001). Most adverse events were mild. One boy in the testosterone group had aggressive behaviour for 1 week after each injection, and one boy in the letrozole group had increased irritability at 6 months.Letrozole might be a feasible alternative treatment to low-dose testosterone for boys with CDGP who opt for medical intervention. However, the risks and benefits of manipulating the reproductive axis during early puberty should be weighed carefully.Helsinki University Hospital, Academy of Finland, and Finnish Foundation for Pediatric Research.

Objective Congenital hypogonadotropic hypogonadism (CHH) is associated with impaired bone mineral density in adulthood, whereas the estimates on bone structure in adolescents with CHH has not been previously evaluated. Design This cross-sectional study describes bone structure in CHH patients and compares it to that in boys with constitutional delay of growth and puberty (CDGP). Methods Peripheral quantitative computed tomography (pQCT) of non-dominant arm and left leg were performed in five treatment-naive males diagnosed with CHH and in 24 males with CDGP. Volumetric bone mineral density (BMD), bone mineral content, and area in trabecular and cortical bone compartments were evaluated, and bone age-adjusted Z-scores for the bone parameters were determined. Results The participants with CHH had more advanced bone age and were older, taller, and heavier than the CDGP boys, yet they had lower trabecular BMD in distal radius (147.7 mg/mm3 [95%CI, 128-168 mg/mm3 ] vs. 181.2 mg/mm3 [172-192 mg/mm3 ], p=0.002) and distal tibia (167.6 mg/mm3 [145-190 mg/mm3 ] vs. 207.2 mg/mm3 [187-227 mg/mm3 ], p=0.012), respectively. CHH males had lower cortical thickness at diaphyseal tibia than the participants with CDGP (p=0.001). These between-group differences remained significant in corresponding Z-scores adjusted for bone age and height (p=0.001). In CDGP group, serum testosterone correlated positively with trabecular BMD (r=0.51, p=0.013) at distal radius, and estradiol levels correlated positively with trabecular BMD at the distal site of tibia (r=0.58, p=0.004). Conclusions Five treatment-naive male patients with CHH exhibited poorer trabecular BMD than untreated males with CDGP. We speculate that timely low-dose sex steroid replacement in CHH males may benefit skeletal health in adulthood.

Background Paternally inherited loss-of-function mutations in MKRN3 underlie central precocious puberty (CPP). We describe clinical and genetic features of CPP patients with paternally inherited MKRN3 mutations in two independent families. Methods The single coding exon of MKRN3 was analyzed in three patients with CPP and their family members, followed by segregation analyses. Additionally, we report the patients' responses to GnRH analog treatment. Results A paternally inherited novel heterozygous c.939C>G, p.(Ile313Met) missense mutation affecting the RING finger domain of MKRN3 was found in a Finnish girl with CPP (age at presentation 6 years). Two Polish siblings (a girl presenting with B2 at the age of 4 years and a boy with adult size testes at the age of 9 years) had inherited a novel heterozygous MKRN3 mutation c.1237_1252delGGAGACACATGCTTTT p.(Gly413Thrfs*63) from their father. The girls were treated with GnRH analogs, which exhibited suppression of the hypothalamic-pituitary-gonadal axis. In contrast, the male patient was not treated, yet he reached his target height. Conclusions We describe two novel MKRN3 mutations in three CPP patients. The first long-term data on a boy with CPP due to an MKRN3 mutation questions the role of GnRH analog treatment in augmenting adult height in males with this condition. Impact We describe the genetic cause for central precocious puberty (CPP) in two families. This report adds two novel mutations to the existing literature. One of the mutations, p.(Ile313Met) affects the RING finger domain of MKRN3, which has been shown to be important for repressing the promoter activity of and . MKRN3KISS1TAC3We describe the first long-term observation of a male patient with CPP due to a paternally inherited MKRN3 loss-of-function mutation. Without GnRH analog treatment, he achieved an adult height that was in accordance with his mid-parental target height.

Paternally inherited loss-of-function mutations in MKRN3 underlie central precocious puberty (CPP). We describe clinical and genetic features of CPP patients with paternally inherited MKRN3 mutations in two independent families.The single coding exon of MKRN3 was analyzed in three patients with CPP and their family members, followed by segregation analyses. Additionally, we report the patients' responses to GnRH analog treatment.A paternally inherited novel heterozygous c.939CG, p.(Ile313Met) missense mutation affecting the RING finger domain of MKRN3 was found in a Finnish girl with CPP (age at presentation 6 years). Two Polish siblings (a girl presenting with B2 at the age of 4 years and a boy with adult size testes at the age of 9 years) had inherited a novel heterozygous MKRN3 mutation c.1237_1252delGGAGACACATGCTTTT p.(Gly413Thrfs*63) from their father. The girls were treated with GnRH analogs, which exhibited suppression of the hypothalamic-pituitary-gonadal axis. In contrast, the male patient was not treated, yet he reached his target height.We describe two novel MKRN3 mutations in three CPP patients. The first long-term data on a boy with CPP due to an MKRN3 mutation questions the role of GnRH analog treatment in augmenting adult height in males with this condition.We describe the genetic cause for central precocious puberty (CPP) in two families. This report adds two novel MKRN3 mutations to the existing literature. One of the mutations, p.(Ile313Met) affects the RING finger domain of MKRN3, which has been shown to be important for repressing the promoter activity of KISS1 and TAC3. We describe the first long-term observation of a male patient with CPP due to a paternally inherited MKRN3 loss-of-function mutation. Without GnRH analog treatment, he achieved an adult height that was in accordance with his mid-parental target height.

STUDY QUESTIONDoes treatment of constitutional delay of growth and puberty (CDGP) in boys with aromatase inhibitor letrozole (Lz) or conventional low-dose testosterone (T) have differing effects on developing seminiferous epithelium?SUMMARY ANSWERAnti-Müllerian hormone (AMH) declined similarly in both treatment groups, and the two Sertoli cell-derived markers (AMH and inhibin B (iB)) exhibited differing responses to changes in gonadotrophin milieu.WHAT IS KNOWN ALREADYBoys with CDGP may benefit from puberty-inducing medication. Peroral Lz activates gonadotrophin secretion, whereas intramuscular low-dose T may transiently suppress gonadotrophins and iB.STUDY DESIGN, SIZE, DURATIONSera of 28 boys with CDGP who participated in a randomised, controlled, open-label trial at four paediatric centres in Finland between August 2013 and January 2017 were analysed. The patients were randomly assigned to receive either Lz (2.5 mg/day) (n = 15) or T (1 mg/kg/month) (n = 13) for 6 months.PARTICIPANTS/MATERIALS, SETTING, METHODSThe 28 patients were at least 14 years of age, showed first signs of puberty, wanted medical attention for CDGP and were evaluated at 0, 3, 6 and 12 months of visits. AMH levels were measured with an electrochemiluminescence immunoassay and Lz levels with liquid chromatography coupled with tandem mass spectrometry.MAIN RESULTS AND THE ROLE OF CHANCEAMH levels decreased in both treatment groups during the 12-month follow-up (P LIMITATIONS, REASONS FOR CAUTIONThe original trial was not blinded for practical reasons and included a limited number of participants.WIDER IMPLICATIONS OF THE FINDINGSIn early puberty, treatment-induced gonadotrophin stimulus was unable to counteract the androgen-mediated decrease in AMH, while changes in iB levels were associated with changes in gonadotrophin levels. AMH decreased similarly in both groups during the treatment, reassuring safety of developing seminiferous epithelium in both treatment approaches. Since a fixed dose of Lz induced variable serum Lz levels with a desired puberty-promoting effect in all boys, more research is needed to aim at a minimal efficient dose per weight.STUDY FUNDING/COMPETING INTEREST(S)This study was supported by the Academy of Finland, the Foundation for Pediatric Research, the Emil Aaltonen Foundation, Sigrid Juselius Foundation and Helsinki University Hospital Research Funds. The authors have nothing to disclose.TRIAL REGISTRATION NUMBERNCT01797718

Background: Aromatase inhibitors (Als) have been used in boys with idiopathic short stature (ISS) to promote growth despite the lack of actual data regarding treatment effect on adult height. In this study, we characterized adult heights and long-term follow-up in Al-treated boys with ISS. Methods: Adult heights and long-term follow-up data, including spine MRIs, of a randomized, double-blind, placebo-controlled trial of boys who were treated with letrozole (Lz) (2.5 mg/d) or placebo (PI) for 2 years during prepuberty and early puberty. The mean bone ages at treatment cessation were 10.2 and 10.8 years, respectively. Results: Adult heights were similar between the boys treated with Lz (n = 10) and those who received PI (n = 10) (164.8 +/- 4.0 vs. 163.7 +/- 3.7 cm, p = 0.49, respectively). In either group, the adult heights did not differ from predicted adult heights at start of the study [PI: 163.7 (3.7) cm vs. 166.9 (3.3), p = 0.06; Lz: 164.8 (4.0) cm vs. 167.6 (7.9), p = 0.20, respectively]. Long-term follow-up data showed that the frequency of subjects with a vertebral deformity was similar between the groups (Lz, 29% and PI, 22%, p = 0.20), and no single comorbidity was clearly enriched in either group. Conclusions: The Lz-treated boys had similar adult heights with the subjects who received PI for 2 years, which indicates that the treatment is not beneficial when given to pre- or early-pubertal boys. Previously observed vertebral deformities ameliorated during follow-up, which supports the skeletal safety of Lz therapy in children and adolescents.

ObjectiveMakorin ring finger protein 3 (MKRN3) gene restrains the hypothalamic–pituitary–gonadal axis. In girls, peripheral levels of MKRN3 decline prior to the onset of puberty. We described longitudinal changes in serum MKRN3 levels in boys before and during puberty and assessed the effect of inhibition of estrogen biosynthesis on MKRN3 levels.DesignLongitudinal serum samples from a double-blind, randomized controlled study in 30 boys (age range: 9.1–14.2years) with idiopathic short stature who received placebo (Pl;n=14) or aromatase inhibitor letrozole (Lz; 2.5mg/day;n=16) for 2years.MethodsWe analyzed the relationships between serum MKRN3 and clinical and biochemical markers of puberty by using summary measures.ResultsSerum MKRN3 declined by 669±713 pg/mL per year (PP<0.05). During G1, MKRN3 levels in Lz-treated subjects decreased slower than in Pl-treated boys (–782±3190 vs –2030±821 pg/mL per year,P<0.05). The decrease in serum MKRN3 levels in G1 was associated with increases in LH (r=–0.5,P<0.01), testosterone (r=–0.6,P<0.01), and inhibin B (r=–0.44,P<0.05) (n=26).ConclusionPeripheral MKRN3 levels in boys appear to serve as a readout of the diminishing central inhibition that controls the onset of puberty.

OBJECTIVE In search of phenotypic cues that would allow early detection of Kallmann syndrome (KS), we evaluated the paediatric phenotypes in a series of females with KS. DESIGN, PATIENTS AND MEASUREMENTS In this retrospective cohort study, we investigated childhood growth in six females with KS due to mutations in FGFR1 and evaluated their reproductive phenotypes later in life. RESULTS While growth during early infancy and childhood was within normal limits, a decreasing trend in height SDS already from mid-childhood occurred in most patients. The lowest height SDS (mean, -1·2 SDS) occurred between 14 and 15 years of age, before the start of hormone replacement therapy. As adults, these women required assisted reproductive techniques for fertility. One of the probands passed on her G48S mutation to her son, who showed normal reproductive hormone levels during the minipuberty of infancy. CONCLUSIONS Early diagnosis of female KS remains a challenge as early phenotypic signs, apart from anosmia, are scarce. Females with KS exhibit a slight reduction in growth rate during mid-childhood, but normal growth rate during the minipuberty of infancy, despite congenital lack of ovarian oestrogen. Women harbouring FGFR1 mutations will have 50% chance of passing on the gene defect to their offspring. We recommend genetic counselling to all females with KS to be carried out as a part of family planning.

STUDY QUESTION What diagnoses underlie delayed puberty (DP) and predict its outcome? SUMMARY ANSWER A multitude of different diagnoses underlie DP, and in boys a history of cryptorchidism, small testicular size and slow growth velocity (GV) predict its clinical course. WHAT IS KNOWN ALREADY DP is caused by a variety of underlying etiologies. Hormonal markers can be used in the differential diagnosis of DP but none of them have shown complete diagnostic accuracy. STUDY DESIGN, SIZE, DURATION Medical records of 589 patients evaluated for DP in a single tertiary care center between 2004 and 2014 were retrospectively reviewed. PARTICIPANTS/MATERIALS, SETTING, METHODS Clinical and biochemical data of 174 boys and 70 girls who fulfilled the criteria of DP were included in the analyses. We characterized the frequencies of underlying conditions and evaluated the predictive efficacy of selected clinical and hormonal markers. MAIN RESULTS AND THE ROLE OF CHANCE Thirty etiologies that underlie DP were identified. No markers of clinical value could be identified in the girls, whereas a history of cryptorchidism in the boys was associated with an increase in the risk of permanent hypogonadism (odds ratio 17.2 (95% CI; 3.4-85.4, P < 0.001)). The conditions that cause functional hypogonadotropic hypogonadism were more frequent in boys with a GV below 3 cm/yr than in those growing faster (19% vs 4%, P < 0.05). In this series, the most effective markers to discriminate the prepubertal boys with constitutional delay of growth and puberty (CDGP) from those with congenital hypogonadotropic hypogonadism (CHH) were testicular volume (cut-off 1.1 ml with a sensitivity of 100% and a specificity of 91%), GnRH-induced maximal LH (cut-off 4.3 IU/L; 100%, 75%) and basal inhibin B (INHB) level (cut-off 61 ng/L; 90%, 83%). LIMITATIONS, REASONS FOR CAUTION The main limitation of the study is the retrospective design. WIDER IMPLICATIONS OF THE FINDINGS Prior cryptorchidism and slow GV are two important clinical cues that may help clinicians to predict the clinical course of DP in boys, whereas markers of similar value could not be identified in girls. In prepubertal boys, testicular size appeared as effective as INHB and GnRH-induced LH levels in the differential diagnosis between CHH and CDGP. STUDY FUNDING/COMPETING INTERESTS This study was supported by the Academy of Finland (268356), Foundation for Pediatric Research (7495), Sigrid Juselius Foundation (2613) and the Finnish Medical Foundation (011115). The authors have no competing interests to report. TRIAL REGISTRATION NUMBER Not applicable.

We describe childhood growth patterns in a series of well-characterized patients with congenital hypogonadotropic hypogonadism (CHH) with special emphasis on genotype–phenotype correlation. We retrospectively evaluated the growth charts of 36 males with CHH (27 from Finland and 9 from Denmark). Fifteen patients (42%) had representative growth measurements during the first year of life. Genetically verified diagnosis of CHH was made in 15 (42%) patients (KAL1, FGFR1, GNRHR, or PROK2). We found a deceleration of growth rate during early childhood. The mean (SD) length standard deviation score (SDS) at birth (0.2 (1.6) SDS) decreased significantly during the first 3 (to −0.9 (1.2) SDS) and 6 mo of life (to −0.7 (1.3) SDS). At the average age of 3 y, mean height SDS (−0.2 (1.3) SDS) did not differ from mid-parental target height (MPH). Mean height SDS reached its nadir (−1.7 (1.4) SDS) at an average age of 15.8 (0.8) years reflecting pubertal failure. Final heights did not differ from MPH. No clear genotype-growth associations emerged. Moderate postnatal length deflection is a novel feature of CHH and may reflect early androgen deficiency. Childhood growth patterns are not of clinical value in targeting molecular genetic diagnosis of CHH.

The initiation of puberty is dependent on loosening of the influence of inhibitory factors acting on the GnRH neurons, which control the hypothalamic-pituitary-gonadal (HPG) axis activity. One of these factors was identified recently, as loss-of-function mutations in the maternally imprinted MKRN3 gene were implicated in central precocious puberty (CPP).(1) MKRN3 encodes Makorin RING-finger protein 3, a putative E3 ubiquitin ligase belonging to the Makorin family of zinc-finger proteins. Recently, circulating MKRN3 was measured in humans for the first time.(2) MKRN3 levels declined prior to clinical onset of puberty and correlated negatively with gonadotropins in prepubertal girls, lending support to the view that a decline in MKRN3 expression precedes the onset of puberty, and circulating MKRN3 reflects this phenomenon. To date it is not known whether circulating MKRN3 in males could serve as a marker of HPG axis integrity. This article is protected by copyright. All rights reserved.