Precocious and Early Central Puberty in Children With Pre-existing Medical Conditions: A Single Center Study

Background: Precocious and early puberty are reported findings in children with pre-existing medical conditions including certain syndromes. Series pertaining to such situations are limited. Methods: A retrospective, single-center study was conducted on children with central precocious puberty (onset before the age of 8 years in girls and 9 years in boys) or early puberty (onset between 8 and 9 years in girls and between 9 and 10.5 years in boys) diagnosed on the background of a known pre-existing chronic significant medical condition. Patients with a CNS tumor and those exposed to cranial irradiation were excluded. Results: Precocious puberty was diagnosed in 13 patients and early puberty in 12. Mean age at onset of puberty was 6.65 ± 2.3 years in girls (n = 15) and 9.4 ± 0.84 years in boys (n = 10). The most common disorders were psychomotor delay (n = 12), psychiatric disorders (n = 7) and/or epilepsy (n = 5). Precocious or early puberty was among the symptoms experienced by patients with a variety of syndromes including lipofuscinosis (2 siblings), Dravet syndrome and Silver-Russel syndrome. Pituitary stalk interruption with agenesis of olfactory bulbs and optic nerve atrophy was found on imaging in one patient who presented with blindness, epilepsy, and autism spectrum disorder. The other diseases associated with precocious or early puberty are adrenocorticotropic deficiency, dyspraxia and bone abnormalities, glomerulopathy with complete renal failure, and repeated intra-fetal deaths in the mother. Karyotype analysis revealed chromosomal duplication (chromosome 15 in 2 cases; chromosomes 17 and 11 in one case each) in 4 of 8 patients evaluated. Conclusions: Data from patients with complex disease who experience precocious or early puberty may provide clues regarding the genetic determinants of pubertal development.


INTRODUCTION
The onset of puberty is driven by an increase in amplitude and frequency of gonadotropin-releasing hormone (GnRH) pulses after a quiescent period during childhood. The reactivation of pulsatile GnRH secretion leads to increases in the secretion of the gonadotropins, luteinizing hormone (LH), and folliclestimulating hormone (FSH) by the anterior pituitary gland and consequent activation of gonadal function (1). Patients experiencing pubertal development as a result of the activation of the hypothalamic-pituitary-gonadal axis before the ages of 8 years (girls) or 9 years (boys) are diagnosed with central precocious puberty (CPP) (2). Those experiencing this activation between the ages of 8-9 years (girls) (3) and 9-10.5 years (boys) (4) are known to have early puberty, an entity that is frequently considered as a normal variant and yet may underscore significant disease.
Complex interactions among genetic, nutritional, environmental, and socio-economic factors control the onset of normal puberty (5,6). In a previous report on 154 patients from 139 families presenting with precocious or early puberty, we were able to demonstrate that the mode of inheritance of either phenotype is predominantly maternal (7). More than half of the families had individuals with either precocious or early puberty, suggesting that both entities may be controlled by similar factors and could likely be studied as a single entity in this particular context (7).
Precocious or early puberty have also been reported in the context of a variety of pre-existing medical conditions including certain syndromes. Series on this particular presentation were absent until the recent presentation of Canton et al. (8) including 26 patients (representing 17% of their idiopathic CPP) presenting as CPP and at least two additional features and/or conditions, characterizing complex phenotypes. The presence of a known, pre-existing, medical diagnosis provides the opportunity to further study potentially contributing factors to precocious or early puberty and shed additional light on the mechanisms of pubertal onset in this population. To this end, we have summarized in this report clinical, laboratory, imaging, and cytogenetic data from 25 patients presenting with this association. Patients with a central nervous system tumor and those exposed to cranial irradiation were excluded from this study.

Ethics Approval and Consent to Participate
The protocol was approved by the Ethical Review Committee Comité de Protection des Personnes Ile de France III (certificate AC 048). All of the clinical investigations were conducted according to the principles expressed in the Declaration of Helsinki. Written informed consent for the evaluations was Abbreviations: BMI, body mass index; BA, bone age; CPP, central precocious puberty; FSH, follicle-stimulating hormone; GnRH, gonadotropin-releasing hormone; LH, luteinizing hormone; MRI, magnetic resonance imaging; SDS, standard deviation score. obtained from the children's parents and was included in their hospital medical records. No additional activity to routine patient care was performed. The authors had no direct interaction with the patients enrolled in the study, except for their medical followup, which was performed by R. Brauner.

Patients
This retrospective, single-center, cohort study included all patients monitored for precocious or early puberty in the context of a pre-existing chronic significant medical condition by a senior pediatric endocrinologist (R. Brauner) in a university pediatric hospital between 2004 and 2014. In girls, CPP was diagnosed by breast development before the age of 8 years accompanied by the presence of pubic or axillary hair, a growth rate >2 SD scores (SDS) the year before clinical evaluation and/or a bone age (BA) >2 years above chronological age (6). In boys, CPP was diagnosed by testicular enlargement (testicular volume index >3.5-4 cm 2 ) before the age of 9 years (2). Early puberty was diagnosed by the appearance of these signs between the ages of 8 and 9 years in girls (3) and 9 and 10.5 years in boys (4). A total of 15 girls and 10 boys fulfilled the diagnostic criteria to be included in this study.

Methods
The initial evaluation included the determination of birth data, height expressed as SDS, growth rate, weight, body mass index (BMI) (expressed as SDS), pubertal stage rated according to Marshall and Tanner and BA assessed using the Greulich and Pyle method (9-11) except in 7 (28%) patients. Age at the first pubertal sign was reported by the parents.
The GnRH test, consisting of the intravenous injection of GnRH (100 µg/m 2 ) and measurements of LH and FSH peaks at 0, 30, 60, and 90 min, was performed in 9 girls and 9 boys. Plasma LH, FSH, estradiol and testosterone concentrations were measured using radioimmunoassay. The following values were considered to be pubertal: LH/FSH peak ratio after GnRH test ≥ 0.66 in girls and ≥ 2 in boys (12), plasma estradiol concentrations ≥ 15 pg/mL in girls and testosterone levels ≥ 0.5 ng/mL in boys. Pelvic ultrasound evaluation was performed in 7 girls to evaluate the estrogenic stimulation of the uterus and to determine GnRH analog treatment. A uterus length value ≥35 mm was considered to be pubertal (13). Magnetic resonance imaging (MRI) was performed to exclude hypothalamic-pituitary lesion. It was not performed in 3 girls with CPP because they had a normal neurological evaluation, were >6 years of age at the onset of puberty and had low plasma estradiol concentration (<15 pg/mL, cases 6 and 8) or because MRI has already been performed in the brother (case 9). Plasma 17-hydroxyprogesterone and testosterone concentrations were measured in all of the boys and in the girls with pubic or axillary hair development as the first pubertal sign to exclude abnormal androgen secretion and congenital adrenal hyperplasia (14). Plasma thyroxin and thyroid-stimulating hormone concentrations were measured to exclude hypothyroidism, and 24-h urinary cortisol levels were measured to exclude hypercortisolism in those who were overweight or had a rapid weight increase; all of the values were normal. Karyotype analysis was performed in 6 girls and 2 boys in the medical follow-up of their pre-existing medical condition.
The results are expressed as the means ± SD.

Characteristics of the Patients
The characteristics of the 25 patients at the initial evaluation are shown in Table 1. Fifteen girls and 10 boys were included in this study, corresponding to a sex ratio at 1.5. Mean age at onset of puberty was 6.65 ± 2.3 years in girls and 9.4 ± 0.84 years in boys.
In girls, the age at onset of puberty was <3 years in 2 patients (13.3%), 3-7 years in 4 patients (26.6%), 7-8 years in 4 patients (26.6%), and 8-9 years in 5 patients (33.3%). In boys, the age at onset of puberty was 8-9 years in 3 patients (30.0%) and 9-10.5 years in 7 patients (70.0%). Thus, 66.5% of the girls and 30% of the boys have CPP, the others having early puberty. LH/FSH peak ratio was pubertal in 6 girls (66.6% of those evaluated) and in 7 boys (77.8%). Bone age was advanced over chronological age by 0.5 ± 0 years in girls and 0.85 ± 0.9 years in boys. One girl (case 1) experienced the onset of breast and pubic hair development at the age of 0.5 years. Pubertal development remained stable without treatment until the age of 8 years when breast and plasma estradiol concentration increased. Five girls (30.0%) and six boys (60.0%) received GnRH agonist treatment. Consanguinity was reported in one case (case 2) without any additional details. A history of familial precocious or early puberty was reported in 8 cases (5 girls and 3 boys); it affected the mother in 6 cases and an older sister in 2 cases ( Table 2).

Pre-existing Medical Diagnoses Associated With Precocious or Early Puberty
In all of the patients, the diagnosis of the associated disorder was made before that of precocious or early puberty, except in case 25 with glomerulopathy and complete renal failure that required renal transplantation, who was diagnosed during the evaluation of early puberty by systematic urinary analysis.
Clinical, MRI and cytogenetic (karyotype) findings are detailed in Table 2. The most common associated medical   ), and glomerulopathy with complete renal failure (case 25). The remaining patient (case 6) had no known pre-existing medical diagnosis but her mother experienced 4 pregnancies complicated by 4 intra-fetal deaths in the mother.
Karyotype analysis revealed abnormalities in 4 of the 8 patients in whom these data were available. These were chromosomal duplications (chromosome 15 in 2 cases, 17 and 11 in one case each). All patients with chromosomal abnormalities had psychomotor delay.

DISCUSSION
Despite the data suggesting that age at the onset of puberty is primarily driven by genetic factors, the genetic determinants of the timing of pubertal development and particularly of precocious or early puberty remain unknown in a majority of cases (15)(16)(17).
In our best knowledge, only one multicentric series of 26 patients presenting as CPP and at least two additional features and/or conditions has been reported in 2018 as an Abstract by Canto et al. (8). They represent 17% of their idiopathic CPP, while the girls of the present study represent 4.5% (10/219) of those seen for CPP in the same conditions. Their most clinical features were: overweight or obesity (n = 15), born small for gestational age (n = 10), learning difficulties/intellectual disability/autistic spectrum (n = 7), short stature (n = 7), motor and/or speech delay (n = 6), high palate (n = 6), acanthosis nigricans (n = 5), and hyperinsulinemia (n = 5). Five patients were previously diagnosed with Temple syndrome (uniparental disomy of chromosome 14), Williams syndrome (7q11.23 microdeletion) or deletions in SHOX (n = 3).
Our study findings suggest that the association between precocious or early puberty and a variety of pre-existing medical conditions may provide additional insight. Indeed, out of 8 patients presenting with psychomotor delay on whom cytogenetic data were available, 50% had chromosomal duplications. Extensive efforts have been made to elucidate the mechanisms that reactivate pulsatile GnRH secretion at the time of puberty, and several genes have been identified in the complex network of inhibitory, stimulatory and permissive neuroendocrine factors involved in the control of puberty onset ( Table 3). In the last decade, the kisspeptin system was revealed as a major gatekeeper of puberty onset (55). Several loss-offunction mutations in KISS1R were described in patients with congenital isolated hypogonadotropic hypogonadism (56). Only two mutations related to this pathway-one mutation in the gene encoding kisspeptin-1 and one in the gene encoding its receptor-have been associated with CPP (18,19).  (22,57). Interestingly, this gene is located in the Prader-Willi syndrome critical region; patients with Prader-Willi syndrome typically have incomplete sexual development; however, few cases of children with CPP have been reported (31)(32)(33)(34).
The association of precocious or early puberty with syndromes and/or medical history is not uncommon and, in most of the cases, the causative factor for this association is unknown. It has been reported in patients with Kabuki syndrome, epidermal nevus syndrome, Cohen syndrome, Williams syndrome, Angelman syndrome, Aicardi syndrome, Floating-Harbor syndrome, cardio-facio-cutaneous syndrome or PEHO syndrome (35)(36)(37)(38)(39)(40)(41)(42)(43)(44)(45)(46). In our series, two siblings diagnosed with lipofuscinosis developed CPP. In the literature, this association has been described in one case report (47) in which the authors suggested that the early onset of puberty could be attributed to selective destruction of inhibitory tracts within the hypothalamus, chronic disruption of GnRH containing neurons or stimulation of gonadotropin release from the pituitary by the accumulation of lipofuscin-like material. CPP has also been associated with neurologic disorders, such as Dravet syndrome, Rett syndrome, neonatal encephalopathy or epilepsy (48)(49)(50)(51)(52)(53)(54). In our series, neurological and/or psychiatric disorders affected most of the patients. This observation is consistent with the findings reported in the literature; in nearly all of the chromosomal abnormalities or the syndromes mentioned above, the patients suffered from neurological disorders, including psychomotor delay, epilepsy, and encephalopathy. Epilepsy and CPP may also co-occur in the context of a central nervous system tumor or insult (58) which should be ruled out via appropriate imaging (59). There have been studies suggesting that valproic acid or other antiepileptic agents, such as clonazepam, could contribute to precocious or early puberty; so far, no evidence could be found in the literature (60)(61)(62). A lot of patients in the present study received various seizure medications.

LIMITATIONS AND STRENGTHS
The 25 patients constitute a small series. However, they were collected over 10 years by one senior pediatric endocrinologist, and no other series had been reported until that of the Sao Paulo University hospital group who reported recently 26 patients (8). We included patients with precocious or early puberty because, as reported in the familial forms, including our series (7), the families frequently include both entities suggesting that they may be controlled by similar factors. Only a small number of patients had a karyotype. The patients of this series are followed by other pediatric specialist, mainly neurologist who posed the indication of the karyotype and sent the patients to us because their pubertal development began early. The Sao Paulo group reported only two patients evaluated for karyotype (See above) (8). Furthermore, as most of the patients were referred to us by a pediatric neurologist, that could explain why so many of the patients had psychomotor delay and/or epilepsy. This could affect the generalizability of the findings of the present study.

CONCLUSION
Although our cohort included a small number of patients, this study is the first, to our knowledge, to describe in detail a series of patients with precocious or early puberty occurring in the context of a pre-existing medical diagnosis. The majority of patients included in this study presented neurological and/or psychiatric disorders, some fulfilling the diagnostic criteria of a syndrome, and others not. Surprisingly high rates of chromosomal abnormalities were found in assessed patients. Additional studies are needed to investigate the mechanisms through which precocious or early puberty is triggered in patients with complex medical histories.

AUTHOR CONTRIBUTIONS
SW collected and analyzed the data and prepared the manuscript. AD collected and analyzed the data. RB directed the work, participated to the preparation and edited the manuscript according to the questions of the Reviewers. All authors discussed the results, commented on the manuscript, and approved the final version to be submitted.