Arginine and clonidine stimulation tests for growth hormone deficiency revisited--do we really need so many samples?

Growth Hormone Stimulation Testing: To Test or Not to Test? That Is One of the Questions

The evaluation of children with short stature includes monitoring over a prolonged period to establish a growth pattern as well as the exclusion of chronic medical conditions that affect growth. After a period of monitoring, evaluation, and screening, growth hormone stimulation testing is considered when the diagnosis of growth hormone deficiency (GHD) is entertained. Though flawed, growth hormone stimulation tests remain part of the comprehensive evaluation of growth and are essential for the diagnosis of growth hormone (GH) deficiency. Variables including testing length, growth hormone assay and diagnostic cut off affect results. Beyond the intrinsic issues of testing, results of GH stimulation testing can be influenced by patient characteristics. Various factors including age, gender, puberty, nutritional status and body weight modulate the secretion of GH.

Diagnosing Growth Hormone Deficiency: Can a Combined Arginine and Clonidine Stimulation Test Replace 2 Separate Tests?

OBJECTIVE

Given the large number of false-positive growth hormone deficiency (GHD) diagnoses from a single growth hormone (GH) stimulation test in children, 2 different pharmacologic tests, performed on separate days or sequentially, are required. This study aimed to assess the reliability and safety of a combined arginine-clonidine stimulation test (CACST).

METHODS

This was a retrospective, single-center, observational study. During 2017-2019, 515 children aged >8 years underwent GH stimulation tests (CACST: n = 362 or clonidine stimulation test [CST]: n = 153). The main outcome measures used to compare the tests were GH response (sufficiency/deficiency) and amplitude and timing of peak GH and safety parameters.

RESULTS

Population characteristics were as follows: median age of 12.2 years (interquartile range [IQR]: 10.7, 13.4), 331 boys (64%), and 282 prepubertal children (54.8%). The GHD rate was comparable with 12.7% for CACST and 14.4% for CST followed by a confirmatory test (glucagon or arginine) (P = .609). Peak GH was higher and occurred later in response to CACST compared with CST (14.6 ng/mL [IQR: 10.6, 19.4] vs 11.4 ng/mL [IQR: 7.0, 15.8], respectively, P < .001; 90 minutes [IQR: 60, 90] vs 60 minutes [IQR: 60, 90], respectively, P < .001). No serious adverse events occurred following CACST.

CONCLUSION

Our findings demonstrate the reliability and safety of CACST in detecting GHD in late childhood and adolescence, suggesting that it may replace separate or sequential GH stimulation tests. By diminishing the need for the second GH stimulation test, CACST saves time, is more cost-effective, and reduces discomfort for children, caregivers, and medical staff.

Peak Growth Hormone Response to Combined Stimulation Test in 315 Children and Correlations with Metabolic Parameters

BACKGROUND/AIMS

Studies are lacking regarding the timing of peak growth hormone (PGH) response. We aim to elucidate the timing of PGH response to arginine and levodopa (A-LD) and evaluate the influence of body mass index (BMI) and other metabolic parameters on PGH.

METHODS

During growth hormone (GH) stimulation testing (ST) with A-LD, serum GH was measured at baseline and every 30 min up to 180 min. The PGH cut-off was defined as &amp;#x3c;10 ng/mL. IGF-1, IGF BP3, BMI, and metabolic parameters were obtained in a fasting state at baseline.

RESULTS

In the 315 tested children, stimulated PGH levels occurred at or before 120 min in 97.8% and at 180 min in 2.2%. GH area under the curve (AUC) positively correlated with PGH in all patients and with IGF-1 in pubertal males and females. BMI negatively correlated with PGH in all subjects. GH AUC negatively correlated with HOMA-IR and total cholesterol.

CONCLUSION

We propose termination of the GH ST with A-LD at 120 min since omission of GH measurement at 180 min did not alter the diagnosis of GH deficiency based on a cut-off of &amp;#x3c; 10 ng/mL. BMI should be considered in the interpretation of GH ST with A-LD. The relationships between GH AUC and metabolic parameters need further study.

TIMING OF GH PEAK IN BOTH GLUCAGON AND CLONIDINE TESTS IS OF MAJOR CLINICAL IMPORTANCE

Objective: To detect a possible correlation between timing of the peak value of growth hormone (GH) during stimulatory tests (STs) and the effectiveness of treatment with recombinant human growth hormone (rhGH) in children with idiopathic GH deficiency (iGHD). Methods: We retrospectively studied 92 patients with iGHD (57 boys; mean age at diagnosis: 9.93 years). Diagnosis was confirmed by 2 different STs, glucagon stimulation test (GST), and clonidine stimulation test (CST). Auxologic parameters were recorded, while observed and predicted (according to KIGS Prediction Model) height velocity during the first year of treatment and the index of responsiveness (IoR) were calculated for the prepubertal children (n = 65). Results: Atypical GST was defined as that with peak GH value at time 0 minutes, 30 minutes, 60 minutes, or 180 minutes, whereas atypical CST was defined as that with peak timing at 0 minutes, 30 minutes, or 120 minutes. Atypical GST was detected in 18 patients (19.57%). IoR was lower in the prepubertal children with atypical GST (-1.81 ± 0.67 versus -1.34 ± 0.85; P = .051). In the CST, the 18 children who had atypical timing, had significantly lower IoR (-1.86 ± 0.66 versus -1.35 ± 0.84; P = .047). When the patients were categorized according to the number of atypical tests, significant differences in the IoR were detected (-2.09 ± 0.68 with 2 atypical STs [n = 6], -1.64 ± 0.61 with 1 atypical ST [n = 16], and -1.29 ± 0.87 with no atypical ST [n = 43], P = .045). Conclusion: The presence of atypical peak GH timing during ST may be a factor that predicts lower growth hormone velocity during the first year of rhGH treatment in prepubertal children with iGHD. Abbreviations: CST = clonidine stimulation test; GH = growth hormone; GHD = growth hormone deficiency; GST = glucagon stimulation test; iGHD = idiopathic growth hormone deficiency; IoR = index of responsiveness; rhGH = recombinant human growth hormone; SDS = standard deviation scores; ST = stimulatory test.

Clonidine Stimulation Test: Is Single Best Time Point, Convenient Yet Efficacious?

CONTEXT

To find a single time point during clonidine stimulation test (CST), with highest diagnostic value to rule out growth hormone deficiency (GHD).

SETTINGS AND DESIGN

This is a retrospective study of 79 CSTs carried out in a tertiary care center in India.

MATERIALS AND METHODS

A cohort of 79 children with unexplained short stature was divided into two groups: GHD and non-GHD. Any one stimulated growth hormone (GH) level >10 ng/mL was used to rule out GHD. Diagnostic accuracy of not only single time points but also time points in pairs was calculated.

STATISTICAL ANALYSIS

The data were analyzed using SPSS statistical software 22.0. Descriptive statistics were used for analyzing demographic data. Mode for time to peak GH was calculated in each group. The specificity and false positive rates at each time point as well as combined time points were determined.

RESULTS

Assaying a single sample at 60 min after clonidine resulted in 20.5% false positive tests with specificity of 79.5%. Addition of the 90 min sample increased specificity to 92.3%.

CONCLUSION

The 60 min sample after clonidine stimulation was the best single sample to rule out GH deficiency. Combined sampling at 60 min + 90 min is economical and less cumbersome, with minimal compromise on the specificity.

Combined simultaneous arginine clonidine stimulation test: Timing of peak growth hormone (GH) concentration and correlation with clinical indices of GH status

BACKGROUND

The aims of this study were to determine if it is possible to truncate a combined simultaneous arginine clonidine stimulation test, and to correlate the outcome of the test with clinical indices of GH status.

METHODS

Charts of subjects who underwent a combined simultaneous arginine clonidine stimulation test between January 1, 2007 and August 31, 2016 were reviewed.

RESULTS

131/203 (64.5%) tests performed in children with growth failure demonstrated a peak GH ≥ 10 ng/ml. 6/7 (85.7%) tests performed in adolescents at the end of GH treatment had a peak GH ≥ 5 ng/ml. Among these negative tests, 97.8% had a passing GH by 120 min. 58/98 (59.1%) tests that had a sample at 150 min were negative. 3/58 (5.2%) had a passing GH level only at 150 min. Therefore, if the test were shortened to 120 min, 5.2% of normal responders would be missed. There was a weak correlation of peak GH with baseline growth velocity and serum IGF-1 z-score. A trend towards an inverse correlation between peak GH level and change in growth velocity pre- and post-GH was seen.

CONCLUSIONS

If the combined simultaneous arginine clonidine test were shortened to 120 min, 5.2% of normal responders would be missed. Although this test has not been compared to any "gold standard" GH stimulation test, the outcome of this test does correlate weakly with clinical indices of GH status and spares patients the inconvenience of sequential testing.

The shortened combined clonidine and arginine test for growth hormone deficiency is practical and specific: a diagnostic accuracy study

BACKGROUND

The growth hormone (GH) stimulation protocols for clonidine and arginine tests are non-standardized and can be lengthy. We examined the specificity of both tests using a shorter duration of timed samples: 90 min for clonidine and 60 min for arginine.

METHODS

We retrospectively studied all children who had GH stimulation with clonidine and arginine to test for GH deficiency (GHD). We compared the diagnostic accuracy of both reference and new shortened test (index).

RESULTS

We reviewed 243 charts (11.4±4.1 years old; 74.5% males). The combined reference test was performed on 159 children, 29 (18.3%) tested positive for GHD on the combined index test, Kappa 0.98, false positive rate 1 (0.8%), specificity 0.99, 95th CI (0.96-1), and p=1.0. The specificity of both the clonidine and arginine single index tests was 0.98%.

CONCLUSIONS

The shortened clonidine and arginine stimulation index tests have good specificity. This is a viable option for testing children for GHD.

CLONIDINE STIMULATION TEST FOR GH DEFICIENCY: A NEW LOOK AT SAMPLE TIMING

OBJECTIVE

In the glucagon stimulation test (GST), the occurrence of peak growth hormone (GH) levels at typical times is an indication of normal secretion. This has not been studied for the clonidine stimulation test (CST). The 120-minute time is rarely the peak, and previous reports suggest it can be omitted. This study aimed to evaluate the meaning and utility of peak time in the CST and the significance of shortening the test.

METHODS

CSTs performed on 250 consecutive subjects in a single center were evaluated for results (GH sufficient or deficient) and result of confirmatory GST with respect to the peak time of the CST.

RESULTS

Peak GH occurred typically at 30, 60, and 90 minutes (91.6% of tests, versus 60% expected) (P<.001). A total of 132 of 155 (85.15%) sufficient tests occurred at typical times, versus 66 of 97 (68%) deficient tests (P<.05). Typicality of timing did not follow in the confirmatory GST and did not predict the final result of testing. Removal of the 120-minute sample affected the final result in 0.4% of evaluations.

CONCLUSION

The timing of the GH peak is not useful when interpreting the CST. The CST is equally effective when terminated at 90 minutes from stimulation.

Clonidine and glucagon stimulation for testing growth hormone secretion in children and adolescents: can we make it with fewer samples?

BACKGROUND

Our aim was to retrospectively evaluate the possibility to reduce the number of GH analyses during clonidine and glucagon tests without compromising accuracy.

SUBJECTS AND METHODS

Two hundred and forty-five tests were performed in a total of 188 children and adolescents with a mean age of 9.93 ± 2.88 yr in a single center during the last 5 yr.

RESULTS

Ninety-one out of 158 (57.59%) clonidine tests and 47/87 (54.02%) glucagon tests had at least one sample >10 μg/l (negative). For clonidine tests, not measuring GH at 30 min would have resulted in only one negative test missed (0.63% false positive result), whereas not measuring GH both at 0 and 30 min would have increased the false positive percentage to 2.53%. Ending clonidine tests at 90 min would have resulted in 7 negative tests missed (4.43% false positive results). For glucagon tests, more than half of the tests peaked at 120 min (56.32%). Skipping sampling at 0, 60 and 180 min provided a false positive rate of 5.75%.

CONCLUSIONS

For clonidine tests we can omit blood sampling at time points 0 and 30 min without significantly compromising accuracy.