The research protocol of this retrospective study was approved by the Ethics Committee of the Children’s Hospital of Nanjing Medical University. The written informed consent for all the subjects to participate in this study was provided by their parents, guardians, or next of kin.
The subjects of this study were 288 young female patients who presented to the Clinic of Pediatric Endocrinology of children’s hospital of Nanjing medical university for evaluation of PP from January 2015 to December 2017. The patients associated with endocrine disorders, previous hormonal therapies, malformations, neurofibromatosis, or congenital adrenal hyperplasia were not included in this study. Finally, among enrolled 288 girls, 133 girls (mean age 6.99 years, range 2.0-8.5) were diagnosed with ICPP, 90 girls (mean age 6.88 years, range 2.5-8.5) were determined to have PT, whereas 35 girls were classified as having early puberty in clinical practice.
The patient’s age, height, weight, growth velocity, bone age, and laboratory testing results were collected. Body mass index (BMI) was calculated by dividing weight in kilograms by height in meters squared.
All the subjects underwent brain MRI with a detailed examination of the pituitary gland at diagnosis. The control group included 30 age-matched girls (mean age 6.90 years, range 5.0-8.0) who underwent MRI for the examination of headaches or seizures rather than breast development.
The clinical diagnostic basis for the ICPP
The diagnosis of ICPP must conform to the diagnosis of CPP, and the pituitary MRI examination is normal. The diagnosis of CPP needs to be consistent with (17): (1) The emergence of secondary sexual characteristics: girls 8 years old, boys 2 years old before the development. The first manifestation was the appearance of breast nodules in girls and increased testicular volume in boys. (2) Linear growth acceleration: The annual growth rate is higher than normal children. (3) Bone age ahead: advanced bone age is 1 year or more than the actual age. (4) Gonadal enlargement: Pelvic ultrasound shows that the uterus and ovaries of the girl increase in volume, and multiple follicles with a diameter of> 4 mm are seen in the ovary; the testicular volume of the boy is> 4 ml. (5) HPGA function starts, serum gonadotropin and sex hormone reach puberty level.
In this study, the diagnosis of CPP was based on the gonadotropin response to a GnRH stimulation test (18). Patients with a peak luteinizing hormone (LH) value of ＞5 IU/L in the GnRH stimulation test were classified as having CPP, whereas those with a peak LH of ＜5 IU/L were classified as having exaggerated thelarche (ET). Notably, the GnRH stimulation test was not performed in the control group, because the GnRH stimulation test is an invasive test and it is meaningless for the undeveloped children.
The clinical diagnostic basis for the PT
The diagnostic criteria of PT are as follows (17): not accompanied by breast development, and is not accompanied by other signs of sexual development, no growth acceleration and early bone development, and without vaginal bleeding. The HPGA function was not activated and the basic values of serum estradiol and follicle-stimulating hormone (FSH) were often slightly increased.
The clinical diagnostic basis for the early puberty
Diagnostic criteria for early puberty are as follows (19): usually, the first 1-2 years of puberty and our study selects girls who have breast development after 8 years of age and the HPGA axis starts, just entering puberty.
MRI was performed on a 1.5-T MRI (1.5T MAGNETOM Symphony, Siemens Healthcare, Erlangen, Germany). The PV was calculated by measuring the length (L), height (H), and width (W) in millimeters of the pituitary. Length and height were determined on the midline sagittal thin section from the posterior wall to the anterior wall. The width was measured on the thin coronal section from anterior to the entrance of the pituitary stalk. Volumes were determined using the ellipsoid formula L*H*W/2 (20, 21). The pituitary shape was visually assessed using the Elster's grade (22), based on the contour of the gland's superior surface in the mid-sagittal projection (grade 1 = marked concavity, grade 2 = mild concavity, grade 3 = flat, grade 4 = mild convexity, grade 5 = marked convexity). In this study, we classified the pituitary shape into 3 grades: concave (grade 1 and grade 2), flat, and convex (grade 4 and grade 5).
GnRH stimulation testing
Regarding the GnRH stimulation test, LH and FSH levels were determined at 0, 30, 60, and 90 minutes after the intravenous injection of 100 μg of compound LH-releasing hormone on Roche E602 using LH electrochemiluminescence detection kit and FSH electrochemiluminescence detection kit in accordance with the kit protocols.
Statistical analysis was performed using SPSS software, version 19.0 (SPSS Inc., Chicago). The data were shown as the mean ± standard deviation (SD). Differences among the different groups were analyzed by one-way analysis of variance (ANOVA), followed by LSD test. Statistical significance was determined as P < 0.05.
For evaluation of the diagnostic value of the PV, receiver operating characteristic (ROC) curve analysis was performed, in which ICPP and PT groups were the dependent variables, whereas the pituitary height, length, width, and volume were the independent variables. The optimal cutoff values were evaluated by using the Youden index (J) (23), which is defined as J=maximum (sensitivity + specificity −1).
Univariate analysis was performed using the Pearson correlation coefficient for continuous variables. Stepwise multivariate regression analysis was performed using peak LH, peak FSH, LH/FSH, age, bone age, and BMI as independent variables and PV as the dependent variable.