Comparison of stimulated growth hormone levels in primed versus unprimed provocative tests. Effect of various testosterone doses on growth hormone levels

Efficacy of short-term induction therapy with low-dose testosterone as a diagnostic tool in the workup of delayed growth and puberty in boys

PURPOSE

Constitutional delay of growth and puberty (CDGP) represents the most frequent cause of delayed puberty in males, sharing some clinical features with growth hormone deficiency (GHD) and isolated hypogonadotropic hypogonadism (IHH). Short-term induction therapy (SIT) has been approved for the induction of puberty in CDGP. We aim to investigate the efficacy of SIT with transcutaneous testosterone gel (TTG) or intramuscular testosterone therapy (IMTT) in a cohort of CDGP subjects, compared to clinical observation. Furthermore, we aim to evaluate the role of SIT as a diagnostic tool to differentiate CDGP from GHD and IHH subjects.

METHODS

The retrospective study included 246 male subjects with delayed puberty. The study population was divided into three groups: TTG, IMTT, and control group (CNT).

RESULTS

At 6 months observation, height velocity (HV) was significantly increased in both treated groups compared to CNT group, particularly higher in TTG than IMTT group. A significant testicular enlargement was revealed in both CNT and TTG group compared to IMTT group. Furthermore, LH value was significantly greater in TTG compared to IMTT group. IGF-1 values after SIT rose significantly in both treated groups compared to CNT group. Moreover, almost all GH provocative tests performed after SIT showed a normal GH response.

CONCLUSION

SIT with TTG appears to be more effective to induce growth spurt, better tolerated and with a more physiological effect on pubertal induction compared to IMTT in CDGP population. Finally, TTG might be a useful tool in the diagnostic work up to discriminate CDGP from GHD or IHH.

Sex steroid priming in short stature children unresponsive to GH stimulation tests: Why, who, when and how

Despite decades of experience, the diagnosis of growth hormone deficiency (GHD) remains challenging, especially in peripubertal children. Failure to respond to GH stimulation tests (GHSTs) is needed to confirm GHD, but long-standing controversies regarding the number of tests needed and the interpretation of GH peaks are still a matter of debate worldwide. Diagnostic workup is even more problematic in short children with slow growth and delayed sexual development: they often exhibit low GH peaks under GHST, which often normalize as puberty progresses. Consequently, this transient suboptimal response to GHST may result in GH overtreatment, carrying both health and economic concerns. Considering the complex and bound link between GH axis and sex steroids, the use of sex steroid priming prior to GHST might be helpful in peripubertal setting. However, its use is still controversial. There is no consensus regarding patient selection, timing, dose, and preparation of sex steroids. In this review, we aim to overview the use of sex steroid priming in clinical practice, highlighting the need to develop appropriate guidelines in order to overcome diagnostic pitfalls in peripubertal age.

Pros of priming in the diagnosis of growth hormone deficiency

Priming with sex steroids in stimulation tests for the diagnosis of GHD is still under debate. Most of the data on utility of priming during GH stimulation so far seem to support its use in the diagnosis of GHD in childhood. There is a propensity to treat growth retarded children who test subnormally to stimulation tests with GH. However, some studies analyzing the final height or height gain during GH treatment in such children failed to show any improvement in height. This paper summarizes previous studies on priming to analyze the utility of priming as a valid method to better the diagnostic capacity of the test.

The relationship between reduced testosterone, stimulated growth hormone secretion and increased carotid intima-media thickness in obese men

OBJECTIVE

Obesity is associated with reduced testosterone and growth hormone (GH). However, the interrelationship between these axes and their independent contributions to cardiovascular risk is unknown. The objectives of this study were to determine (1) the association between testosterone and GH in obesity, (2) whether excess adiposity mediates this association and (3) the relative contribution of reduced testosterone and GH to increased carotid intima-media thickness (cIMT) in obesity.

DESIGN

Fifty obese men were studied with GH-releasing hormone-arginine testing, and morning free testosterone (FT) was measured by equilibrium dialysis. Metabolic, anthropometric and cardiovascular risk indices, including cIMT were measured. Twenty-six normal weight men served as controls.

RESULTS

Obese subjects demonstrated lower mean (±SEM) peak stimulated GH (5·9 ± 0·6 vs 36·4 ± 3·9 μg/l; P < 0·0001) and FT (0·41 ± 0·03 vs 0·56 ± 0·03 nmol/l; P = 0·0005) compared to controls. GH was significantly associated with FT (r = +0·44; P < 0·0001) and both were inversely related to visceral adipose tissue (VAT) (GH: r = -0·65; P < 0·0001; FT: r = -0·51; P < 0·0001). In multivariate regression analysis controlling for VAT, FT was no longer related to GH. Both GH and FT were associated with cIMT in univariate analysis. However, in multivariate modelling including traditional cardiovascular risk markers, GH (β = 0·003; P = 0·04) but not FT (P = 0·35) was associated with cIMT.

CONCLUSIONS

These results demonstrate a strong relationship between FT and GH in obesity and suggest that this relationship is more a function of excess adiposity rather than a direct relationship. While reduced FT and GH are both related to increased cIMT, the relationship with reduced GH remains significant controlling for reduced FT and traditional cardiovascular disease risk markers.

Pharmacological and physiological growth hormone stimulation tests to predict successful GH therapy in children

Although the current use of growth hormone (GH) stimulation tests (GHSTs) is still subject to debate, the tests are widely used to diagnose GH deficiency. This literature review evaluates primarily the sensitivity, specificity and reliability of GHSTs and secondarily their convenience. Single pharmacological tests typically address only a single pathway in the complex physiological regulation of GH secretion and are therefore characterized by lower sensitivity, specificity and reliability than combined pharmacological tests or physiological tests. In spite of the high levels of sensitivity, specificity and reliability, physiological tests require considerably more effort to perform, from the physician as well as from the child. Therefore, a need for an alternative, convenient, physiological GHST still remains. Oral ingestion of dietary protein is convenient in practice and may induce more physiological stimulation of GH secretion, hence may be a promising valuable addition to the existing GHSTs in GH deficiency.

Is testosterone and estrogen priming prior to clonidine useful in the evaluation of the growth hormone status of short peripubertal children?

AIM

To determine the usefulness of priming with gonadal steroids prior to growth hormone (GH) stimulation with clonidine in the evaluation of the GH status of short peripubertal children.

CHILDREN AND METHODS

Thirty-nine children, eight females and 31 males, were studied, with a mean chronological age of 12.37 +/- 2.24 years (range 8-15 years), mean bone age 9.58 +/- 2.21 years, Tanner stage 1-2, with height 134.12 +/- 11.27 cm (Ht-SDS -2.24 +/- 0.95), growth velocity (GV) 4.2 cm/yr (GV SDS -2.12 +/- 1.32) and an inadequate response to an initial GH stimulation test with clonidine (peak GH <10 microg/l). A second stimulation test with clonidine was performed in the same patients after gonadal steroid priming: 100 mg i.m. testosterone enanthate 5-8 days prior to GH stimulation in the males, and 1 mg estradiol valerate daily for 3 days in the females. GH, IGF-I, and testosterone/estradiol were measured before and after priming.

RESULTS

Twenty-one of 39 children (53.8%) increased their GH response to a level of >10 microg/l following priming with gonadal steroids. Mean peak GH after priming was 12.32 +/- 8.7 microg/l compared to a peak GH level of 4.87 +/- 2.72 microg/l prior to gonadal steroid priming (peak GH 17.42 +/- 8.46 microg/l in the responders versus 5.95 +/- 2.76 microg/l in the non-responders). Although a significant increase in GH and IGF-I concentrations was noted following priming, we were unable to find a correlation between IGF-I concentrations and peak GH following priming. IGF-I levels were not different in the responders and non-responders to clonidine following priming. There was no correlation between pubertal staging and testosterone/estradiol concentrations before priming with the peak GH after priming.

CONCLUSIONS

Priming with gonadal steroids significantly improves GH secretion following GH stimulation with clonidine and diminishes the possibility of a false diagnosis of GH deficiency. Gonadal steroid priming should therefore be considered in the evaluation of the GH status of short children close to or during the early stages of puberty.

Management of boys with short stature and delayed puberty

OBJECTIVE

To review the management of boys with short stature and delayed puberty and the testosterone priming protocol.

METHODS

In 148 boys aged > 14 years seen for height < -2 SDS and constitutional delayed puberty we evaluated growth hormone (GH) secretion and final height (80 boys).

RESULTS

The GH peak was < 10 microg/l after arginine-insulin tests performed with testosterone heptylate priming in 8/32 (25%) and without in 62/153 (41%), including first and second evaluations. It was low in 7/11 boys given 2 x 100 mg testosterone (14.7 +/- 1.7 microg/l) and in 1/21 given 4 x 100 mg (21.3 +/- 2.0 microg/l, p = 0.04). It was low during sleep in 4/29 (14%) boys, all having basal plasma testosterone below 3.5 nmol/l. The basal insulin-like growth factor (IGF)-I concentration was below -2 SDS in 22% of the boys evaluated. Final height was -0.8 +/- 0.1 SDS. It was similar in those with low (n = 9) and normal (n = 71) GH peak, and in those treated (n = 22) or untreated (n = 58) with testosterone. It was over 1 SDS lower than the target height in 20% and than the predicted height at the initial evaluation in 14% of the boys. Pubertal growth was not correlated with the GH peak or plasma IGF-I.

CONCLUSIONS

The GH peak during the sleep is more frequently normal than the peak after stimulation. The number of testosterone doses influences the quality of priming. The medical problems involved in treating boys with delayed puberty are excluding disease and deciding on testosterone treatment.

Is growth hormone stimulation testing in children still appropriate?

The diagnosis of growth hormone deficiency (GHD) historically has relied on measurement of growth hormone (GH) concentrations following stimulation, usually with a non-physiologic provocative agent. Despite the use of more specific GH assays, the peak concentration of GH below which a child is considered GH deficient has risen. We examine the pitfalls associated with GH stimulation tests, specifically, the lack of reliability and accuracy of these tests, and their inability to predict who will benefit from GH therapy. We recommend that GH stimulation tests no longer routinely be used for the diagnosis of GHD in children.

Rational use of the laboratory for childhood and adult growth hormone deficiency

No laboratory test has sufficient diagnostic sensitivity and specificity to serve as a gold standard for the diagnosis for GHD: therefore, test results must be interpreted after assessment of risk for GHD is determined on clinical grounds. Growth data are particularly crucial for diagnosis of childhood GHD;history of known pituitary damage and presence or absence of other pituitary hormone deficiencies are the critical elements for the diagnosis of adult GHD. New reference preparations are available for GH and IGF-I and should greatly aid interassay comparisons when the preparations are universally adopted.GH stimulation testing remains a key part of the diagnosis of adult GHD, but is currently being de-emphasized for the diagnosis of pediatric GHD. Better interassay comparative data and organized clinical collaboration between clinicians and test manufacturers/laboratories to set rational clinical diagnostic cutoffs would improve greatly the clinical usefulness of GH stimulation testing. The availability of statistically sound age- and sex-related normative data for IGF-I and IGFBP3 make these key tests for the diagnosis of childhood GHD. Although IGF-I may not be a perfect test for the diagnosis of adult GHD, it may be sufficiently informative in many cases to warrant using it ona routine basis. IGF-I also has a role in monitoring the safety of adult patients who are on GH treatment; studies are underway to determine if IGF-I may be useful in the future for optimization of GH dosaging.

Assessing short-statured children for growth hormone deficiency

AIM

To optimize the workup of short-statured children by defining the most appropriate tools for diagnosing growth hormone (GH) deficiency.

METHODS

Patients were assigned to prepubertal (n = 113) or pubertal (n = 112, including 25 boys primed with testosterone) age groups. Mean plasma GH concentration during sleep, GH peak after provocative test, and insulin-like growth factor I (IGF-I) were measured in a single evaluation.

RESULTS

The mean GH concentration during sleep was more often normal (n = 155) than the GH peak after provocative tests (n = 105) or the IGF-I concentration (n = 88). Prepubertal patients with a normal body mass index (BMI) had mean GH concentrations during sleep that correlated positively with height, growth rate, GH peak after provocative tests, and IGF-I (p < 0.0005 for all) and negatively with the difference between target and patient heights (p = 0.01) and BMI (p < 0.05). Pubertal patients with a normal BMI had a mean GH concentration during sleep that correlated positively with GH after provocative tests (p < 0.0001) and IGF-I (p < 0.005). Mean GH concentration during sleep and IGF-I concentration for boys primed with testosterone were more often normal (n = 23) than the GH peak after provocative tests (n = 14). All 9 patients with pituitary stalk interruption had low IGF-I concentrations; 1 patient had a normal GH peak after provocative test, and 2 patients had normal mean GH concentrations during sleep.

CONCLUSIONS

Measuring the GH concentration during sleep and priming boys with pubertal delay can help to exclude idiopathic GH deficiency. Magnetic resonance imaging is needed to exclude anatomic abnormalities when GH and/or IGF-I concentrations are low.

Priming with testosterone enhances stimulated growth hormone secretion in boys with delayed puberty

BACKGROUND AND OBJECTIVE

Tests for growth hormone (GH) deficiency are not always helpful in the differential diagnosis of physiological delay of growth and puberty and GH deficiency.

PATIENTS AND METHODS

To enhance diagnostic specificity, we used a single dose testosterone priming before repeating the arginine stimulation test in 26 boys with short stature and only early signs of puberty who failed to show an adequate response of serum GH in the first test.

RESULTS

77% (20/26 patients) increased their serum GH peak to more than 10 ng/ml, whereas six patients were still below this concentration.

CONCLUSION

We propose that testosterone priming is a useful tool to distinguish between physiological delay of growth and puberty and GH deficiency and should be included in the diagnostic procedure.