Clinical and laboratory characteristics but not response to treatment can distinguish children with definite growth hormone deficiency from short stature unresponsive to stimulation tests

Introduction

It has been proposed that not all children with short stature displaying an inadequate response to tests for growth hormone (GH) secretion truly suffer from GH deficiency (GHD). Only children with a monogenic cause of GHD or an identifiable combined hormonal deficiency or anatomical anomaly in the hypothalamic-pituitary axis should be considered definite GHD (dGHD). The remaining patients can be defined as a separate group of patients, "short stature unresponsive to stimulation tests" (SUS). The aim of this proof-of-concept study, was to assess whether SUS patients treated with rhGH exhibit any differences compared to GHD patients undergoing the same treatment.

Methods

Retrospective analysis on 153 consecutive patients with short stature and pathological response to two GH stimulation tests. Patients with dGHD were defined as those with a clear genetic or anatomical hypothalamic-pituitary anomaly, as well as those with combined pituitary hormone deficiencies and those with a known insult to the hypothalamic-pituitary axis (i.e. total brain irradiation) (n=38, 25%); those without any of the previous anomalies were defined as SUS (n=115, 75%).

Results

At diagnosis, dGHD and SUS populations did not differ significantly in sex (F 32% vs 28%, p=0.68), age (11.9 vs 12.1, p=0.45), height SDS at diagnosis (-2.2 vs. -2.0, p=0.35) and prevalence of short stature (height <-2 SDS) (56% vs 51%, p=0.45). IGF-1 SDS were significantly lower in dGHD (-2.0 vs -1.3, p<0.01). After 1 year of treatment, the prevalence of short stature was significantly reduced in both groups (31% in dGHD vs. 21% in SUS, p<0.01) without any significant differences between groups (p=0.19), while the increase in IGF-1 SDS for bone age was greater in the dGHD category (+1.9 vs. +1.5, p<0.01), with no further difference in IGF-1 SDS between groups. At the last available follow-up, 59 patients had reached the near adult height (NAH) and underwent retesting for GHD. No differences in NAH were found (-0.3 vs. -0.4 SDS, 0% vs. 4% of short stature). The prevalence of pathological retesting was higher in dGHD (60% vs. 10%, p<0.01) as well as of overweight and obesity (67% vs. 26%).

Conclusion

Stimulation tests and the equivalent benefit from rhGH therapy, cannot distinguish between dGHD and SUS populations. In addition, lower IGF-1 concentrations at baseline and their higher increase during treatment in dGHD patients, and the lack of pathological retesting upon reaching NAH in SUS patients, are facts that suggest that deficient GH secretion may not be the cause of short stature in the SUS studied population.

Prevalence and characteristics of thelarche variant

Introduction

Girls with early thelarche may show an intermediate clinical picture between isolated premature thelarche (PT) and central precocious puberty (CPP), defined as "thelarche variant" (TV), characterized by an FSH-predominant response, although a univocal definition is lacking.

Methods

Retrospective analysis on 91 girls with early thelarche (<8 years) and advanced bone age and/or accelerated growth who underwent 104 LHRH tests. Patients were classified into CPP (LH peak ≥5 IU/L; n = 28, 31%), TV (FSH peak ≥20 IU/L, LH peak <5 IU/L; n = 15, 16%), or PT (FSH peak <20 IU/L and LH peak <5 IU/L; n = 48, 53%).

Results

TV patients were younger (5.51 years) and with less advanced bone age (+0.8 years). They had higher basal and peak FSH (2.5 and 26.6 IU/L) and lower basal and peak LH/FSH ratios (0.08 and 0.11). The prevalence of presence of ovarian follicles >5 mm in TV (42%) was similar to CPP but significantly higher than PT, whereas maximum ovarian volume was smaller in TV (1.0 cm3). At the last follow-up visit (available in 60% of the cases), 44% of TV developed CPP compared with 14% of PT (p = 0.04). At first evaluation, those who progressed to CPP had a higher basal FSH (3.2 IU/L), lower LH/FSH ratio (0.07), and a higher peak LH (4.1 IU/L) compared with those who did not progress to CPP (basal FSH 1.9 IU/L, p < 0.01; basal LH/FSH ratio 0.12, p < 0.01; peak LH 2.8 IU/L, p = 0.02).

Conclusion

Using laboratory parameters only as a definition, we identified the clinical, laboratory, and imaging features of TV: these girls showed less advanced bone age and FSH predominance also at baseline, with smaller ovaries but with follicles >5 mm. Almost half of girls initially diagnosed as TV developed CPP at last follow-up visit, and these girls had higher baseline FSH, lower baseline LH/FSH ratio, and higher peak LH at first evaluation. Therefore, TV may represent a "precocious prepuberty" in which the FSH predominance may initially limit the progression into proper puberty, but it may eventually trigger full puberty (even CPP, depending on the girls' age).

Should Pediatric Endocrinologists Consider More Carefully When to Perform a Stimulation Test?

INTRODUCTION

Pediatric endocrinology rely greatly on hormone stimulation tests which demand time, money and effort. The knowledge of the pattern of pediatric endocrinology stimulation tests is therefore crucial to optimize resources and guide public health interventions. Aim of the study was to investigate the distribution of endocrine stimulation tests and the prevalence of pathological findings over a year and to explore whether single basal hormone concentrations could have saved unnecessary stimulation tests.

METHODS

Retrospective study with data collection for pediatric endocrine stimulation tests performed in 2019 in a tertiary center.

RESULTS

Overall, 278 tests were performed on 206 patients. The most performed test was arginine tolerance test (34%), followed by LHRH test (24%) and standard dose Synachthen test (19%), while the higher rate of pathological response was found in insulin tolerance test to detect growth hormone deficiency (81%), LHRH test to detect central precocious puberty (50%) and arginine tolerance test (41%). No cases of non-classical-congenital adrenal hyperplasia were diagnosed. While 29% of growth hormone deficient children who performed an insulin tolerance test had a pathological peak cortisol, none of them had central adrenal insufficiency confirmed at low dose Synacthen test. The use of basal hormone determinations could save up to 88% of standard dose Synachthen tests, 82% of arginine tolerance + GHRH test, 61% of LHRH test, 12% of tests for adrenal secretion.

CONCLUSION

The use of single basal hormone concentrations could spare up to half of the tests, saving from 32,000 to 79,000 euros in 1 year. Apart from basal cortisol level <108 nmol/L to detect adrenal insufficiency and IGF-1 <-1.5 SDS to detect growth hormone deficiency, all the other cut-off for basal hormone determinations were found valid in order to spare unnecessary stimulation tests.