Claudia Baffoni

Usefulness of IGF-I assay for the diagnosis of GH deficiency in adults

IGF-I is the best marker of GH secretory status but it also depends on the nutritional status and peripheral hormones such as insulin, glucocorticoids, thyroid hormones and gonadal steroids. Though monitoring IGF-I levels is the best way for evaluating appropriate GH replacement, the usefulness of IGF-I assay in the diagnosis of adult GH deficiency (GHD) is still matter of debate. To clarify this point in a large population of GHD adults (no.=135, 61 women and 74 men; age, mean±SE: 43.8±1.4 yr, range 20–80 yr) we studied IGF-I levels, their reproducibility and association to peak GH response to GHRH+arginine (GHRH+ARG) test and insulin tolerance test (ITT). The results in GHD were compared with those in a large population of normal subjects (no.=336, 233 women and 103 men, aged 20–80 yr). Mean IGF-I levels in GHD (77.8±4.9 µg/l) were clearly lower (p<0.001) than those in normal subjects (170.2±4.7 µg/I). In Childhood Onset GHD (CO-GHD; no.=40; age, mean±SE: 27.8±1.5 yr) IGF-I levels were lower than those in Adult Onset GHD (AO-GHD; no.=95, age, mean±SE: 50.7±1.4 yr) (56.6±9.7 vs 87.1 ±5.4 µg/l, p<0.0003). In both GHD and normal subjects IGF-I levels showed good, reproducibility (r=0.92, p<0.00001 and r=0.62, p<0.00001, respectively). In GHD, but not in normal subjects, IGF-I levels were positively associated to peak GH responses to GHRH+ARG (r=0.57, p<0.00001); on the other hand, the GH peak after ITT was not associated to IGF-I in GHD. In normal subjects, but not in GHD, IGF-I levels were negatively associated to age (r=−0.60, p<0.00001). Considering individual IGF-I levels there was a clear overlap between GHD and normal subjects. However, this overlap was strongly dependent on age. In fact, in the third and fourth decade of life 83.6% of GHD had IGF-I levels below the 3rd centile of normal values; on the other hand, in the fifth-sixth decade and in ageing 47% and only 12% of GHD, respectively, had IGF-I levels low for age. In conclusion, our results demonstrate that IGF-I levels represent a reproducible marker of GH status and are reduced more in CO-GHD than in AO-GHD adults. An overlap exists between GHD and normal subjects, however this is small up to the 4th decade of life. Thus, though normal IGF-I levels do not rule out the existence of GHD, up to 40 yr low IGF-I levels strongly point to GHD if malnutrition and liver disease have been ruled out.

Endocrine responses to ghrelin in adult patients with isolated childhood-onset growth hormone deficiency

objective Ghrelin, a 28 amino acid acylated peptide, is a natural ligand of the GH secretagogues (GHS) receptor (GHS‐R), which is specific for synthetic GHS. Similar to synthetic GHS, ghrelin strongly stimulates GH secretion but also displays significant stimulatory effects on lactotroph and corticotroph secretion. It has been hypothesized that isolated GH deficiency (GHD) could reflect hypothalamic impairment that would theoretically involve defect in ghrelin activity.

Short procedure of GHRH plus arginine test in clinical practice

Either in children or in adults, arginine (ARG) alone and combined with GHRH (GHRH + ARG) are reliable tests for the diagnosis of GH deficiency. The procedures of these tests generally include GH measurement every 15 min from baseline up to 90–120 min. Aim of our study was to verify if the procedure of these tests could be usefully shortened in clinical practice. To this goal we have studied 173 normally growing children and adolescents (C, 117 M and 56 F, age: 11.3 ± 0.4 yr.) and 125 young and middle aged normal adults (A, 68 M and 57 F, age: 30.0 ± 0.6 yr.). ARG alone test was performed by 81 C and 33 A (0.5 g/kg arginine, iv, from 0 to +30 min, up to a maximum of 30 g) while GHRH (1 μg/kg iv bolus at 0 min) + ARG test was performed by 92 C and 92 A. After ARG alone, taking into account data from +15 to +105 min, GH values above the 3rd centile limit of arbitrary cut-off (7 or 10 μg/1 in C and 5 μg/1 in A) occurred in 85% or 64% and 94% subjects, respectively. After GHRH + ARG test, taking into account only data at +30, +45, +60 min GH values above the 3rd centile limit (20 μg/1 in C and 16.5 μg/1 in A) occurred in 99% of subjects in both groups. Taking into account only these 3 timing points, the percentage of GH peak above the third centile limits after ARG alone was never higher than 60% in C and 85% in A. In conclusion, this study shows that single GHRH + arginine test can be reliably performed in a shortened procedure which makes easier the clinical practice and further reduces costs.

Silent renal stones in primary hyperparathyroidism: prevalence and clinical features.

OBJECTIVE (1) To evaluate the prevalence of silent nephrolithiasis in patients with primary hyperparathyroidism (PHPT) compared with controls, and (2) To characterize clinically PHPT patients with silent renal stones. METHODS We reviewed clinical data for 141 patients with PHPT and without symptoms or history of nephrolithiasis in whom renal ultrasonography was performed at diagnosis. A total of 141 sex- and age- matched subjects with abdomen ultrasonography obtained for reasons different from urinary symptoms served as controls. RESULTS Silent nephrolithiasis was more prevalent in PHPT patients than in controls (11.35% vs. 2.13%; P = .003). Among patients with PHPT, those with silent renal stones showed higher serum calcium and parathyroid hormone levels and met surgical criteria, regardless of nephrolithiasis, more frequently than those without renal stones. CONCLUSION The prevalence of silent nephrolithiasis is increased in patients with PHPT as compared with controls. Moreover, it seems likely that silent renal stone disease could identify a subset of PHPT patients with more severe disease. Accordingly, we suggest ultrasonographic screening of nephrolithiasis in all PHPT patients. Further studies are needed to better characterize this clinical entity.

Vitamin D status in primary hyperparathyroidism: a Southern European perspective

Vitamin D deficiency (VDD) is common in patients with primary hyperparathyroidism (pHPT), and this could affect the clinical expression of the disease. However, few North American or North European studies have addressed this issue, showing vitamin D repletion in only about one‐third of the patients.

Parathyroidectomy Halts the Deterioration of Renal Function in Primary Hyperparathyroidism

OBJECTIVE Decreased renal function has been consistently included among factors prompting recommendation for surgery in primary hyperparathyroidism (PHPT). However, most retrospective studies addressing this issue did not show an improvement in renal function after parathyroidectomy (PTX). The aim of this study was to investigate changes in renal function after PTX in PHPT patients subdivided according to renal function at diagnosis. DESIGN This was a retrospective cross-sectional study. PATIENTS AND METHODS We studied 109 consecutive PHPT patients before and after PTX. Biochemical evaluation included fasting total and ionized serum calcium, phosphate, creatinine, immunoreactive intact PTH, and 25-hydroxyvitamin D3 levels. Glomerular filtration rate (GFR) was assessed with the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equation. RESULTS Mean (± SD) CKD-EPI estimated GFR (eGFR) at diagnosis was 82.4 ± 19.3 mL/min/1.73 m(2) (median, 84.8 mL/min/1.73 m(2); interquartile range, 68.5-94.2 mL/min/1.73 m(2)). Patients with eGFR equal to or higher than 60 mL/min/1.73 m(2) (group 1, n = 95) were significantly younger than patients with eGFR lower than 60 mL/min/1.73 m(2) (group 2, n = 14; P < .0003). After PTX, eGFR did not change in patients of group 2 (P = .509), whereas it was significantly reduced in patients of group 1 (P < .0002). The difference in eGFR between baseline and post-PTX values was correlated negatively with baseline serum creatinine (R = -0.27; P = .0052) and positively with baseline CKD-EPI eGFR (R = 0.32; P = .00062). At multiple regression analysis, only systolic blood pressure and baseline CKD-EPI eGFR were independent predictors of GFR variation. CONCLUSION Surgical cure of PHPT halts renal function deterioration in patients with coexisting renal disease. Our study thus supports the indication for surgery in patients with eGFR less than 60 mL/min/1.73 m(2), as recommended by current guidelines. Moreover, our data show that presurgical renal function is a relevant predictor of renal function after PTX.

Hypopituitaric patients with corticotropin insufficiency show marked impairment of the cortisol response to ACTH (1-24) independently of the duration of the disease

It is widely accepted that the classical dose of 250.0 μg ACTH (1–24) (tetracosactin) is clearly supra-maximal while 1.0 and 0.03 μg have been shown as the maximal and the lowest stimulatory ACTH doses for cortisol (F) secretion in normal young subjects. Testing with low ACTH dose would better evaluate adrenal sensitivity to corticotropin. The aims of the present study were: a) to clarify the adrenal sensitivity to ACTH in patients with different duration of corticotroph insufficiency by testing with low and very low tetracosactin doses; and b) to evaluate diagnostic implication regarding the ability of ACTH tests to distinguish patients with corticotroph insufficiency from normal subjects. In 24 hypopituitaric patients (HYPOPIT, 15 male and 9 female, age 22–50 yr, BMI: 22–26 kg/m2) with corticotrophin deficiency we studied the F, DHEA and aldosterone (A) responses to challenges with low ACTH doses (0.06 or 0.5 μg iv at 0 min) followed by 250 μg iv (at +60 min). The results in HYPOPIT were compared with those recorded in 12 normal controls (NS, 6 male and 6 female, age 22–34 yr, BMI: 20–25 kg/m2). Basal F and DHEA levels in HYPOPIT were lower than in NS, while A levels were similar in both groups. The F responses to ACTH in HYPOPIT were dose-independent and markedly lower (p<0.0001) than in NS. After the 0.06 and 0.5 μg ACTH dose, 16% of HYPOPIT patients showed δF peak within the range of normal response. No HYPOPIT showed δF peak within the normal range after 250 μg ACTH. The DHEA responses to ACTH in HYPOPIT were dose-independent and markedly lower than in NS (p<0.0001). Overlap between individual DHEA responses in HYPOPIT and NS was present after 0.06 μg and 0.5 μg but not after 250 μg tetracosactin. The A responses in HYPOPIT were dose-dependent and overlapped with those in NS. The adrenal responses to ACTH in HYPOPIT were not associated with the duration of the disease. In conclusion, the present study shows that the mean F and DHEA but not the A responses to ACTH (1–24) are markedly impaired in hypopituitaric patients with corticotroph insufficiency independently of the duration of the disease. The impaired F and DHEA response to ACTH is also independent of the dose, suggesting the existence of relatively enhanced sensitivity of the fasciculata and reticularis adrenal zone to ACTH but meantime remarkable impairment of the adrenal function due to corticotrophin deficiency. In the present study, testing with submaximal ACTH doses did not distinguish patients with secondary adrenal insufficiency from normal subjects.

DHEA-S levels in hypopituitaric patients with severe GH deficiency are strongly reduced across lifespan. Comparison with IGF-I levels before and during rhGH replacement.

Both IGF-I and DHEA-S undergo an age-related decrease and their decrease could be involved in age-related changes in body composition, structure functions and metabolism. On the other hand, it is well known that mean IGF-I levels are clearly reduced in hypopituitaric patients with GH deficiency (GHD) while data about dehydroepiandrosterone sulfate (DHEA-S) levels in hypopituitarism are scanty. We evaluated DHEA-S and IGF-I levels and their relationship in 90 patients with panhypopituitarism (HYPOPIT) with severe GHD [49 women and 41 men; age, mean±SE: 47.9±1.49 yr, range: 20-80 yr; BMI: 26.4±0.6 kg/m2; 21 with childhood-onset (CO) and 69 with adult-onset (AO) HYPOPIT]. DHEA-S and IGF-I levels were also evaluated in 24 HYPOPIT with GHD after 3-month recombinant human GH (rhGH) replacement. Data in HYPOPIT were compared with those in a large group of healthy controls (NS, 233 women and 103 men, aged 20–80 yr; all subjects were within ±15% of their ideal body weight). In NS both DHEA-S levels and IGF-I were gender-independent while showed a strong, inverse correlation with age (r=-0.6; p<0.001 and r=-0.56; p<0.0001, respectively). Nevertheless, no relationship was found between DHEA-S and IGF-I levels in NS. In HYPOPIT, age-adjusted mean DHEA-S and IGF-I levels were clearly lower than those in NS (2.3±0.4 vs 16.0±0.7 μg/l, p<0.005; 71.1±4.5 vs 170±4.7 μg/l, p<0.005). IGF-I levels in CO-HYPOPIT were lower (p<0.01) than those in AO-HYPOPIT (49.6±4.8 vs 77.0±5.4 μg/l), while DHEA-S levels were similar in both subgroups (2.6±0.7 vs 2.3±0.4 μg/l). In HYPOPIT both DHEA-S and IGF-I were independent of age and gender while there was a trend toward a positive association between each other (r=0.45; p<0.003). Analyzing individual levels in HYPOPIT with respect to age-adjusted normal ranges, IGF-I levels were below normal in 84, 62 and 0% between 20–40, 40–60 and 60–80 yr, respectively. On the other hand, DHEA-S levels were below normal in 84, 86 and 67% between 20–40, 40–60 and 60–80, respectively. In HYPOPIT rhGH treatment strikingly increased IGF-I levels (150±3.2 vs 85.3±4.1 μg/l, p<0.005) while did not modify DHEA-S levels (1.7±0.2 vs 1.6±0.2 μg/l). In conclusion, our results demonstrate that DHEA-S and IGF-I are negatively and independently associated to age in physiological conditions but not in hypopituitaric patients in whom both are strikingly reduced. Both DHEA-S and IGF-I levels in HYPOPIT show some overlap with those in normal subjects; thus the assay of these parameters is not diagnostic for hypopituitarism. DHEA-S reduction in HYPOPIT does not depend on IGF-I as indicated also by evidence that GH replacement restores IGF-I but does not modify DHEA-S levels.

Reduction of the pituitary GH releasable pool in short children with GH neurosecretory dysfunction

OBJECTIVES The classical ‘GH neurosecretory dysfunction’ (GHNSD) refers to slowly growing children with normal GH responses to classical provocative tests but impaired spontaneous GH secretion over 24 h frequently leading to low IGF‐I levels. Thus it has been assumed that these subjects have insufficiency of spontaneous GH secretion due to neuroendocrine abnormalities in spite of a normal releasable pool of GH. However, classical provocative tests do not reliably assess the maximal somatotroph capacity; thus it is still unclear if the GH pool is really preserved or not. GHRH + arginine test is more potent than the classical tests and evaluates the maximal secretory capacity of somatotroph cells. The GH response to this stimulus is reproducible and also independent of age and puberty.

Sequential administration of arginine and arginine plus GHRH to test somatotroph function in short children

The hormonal diagnosis of GH deficiency in childhood is conventionally based on the GH response to at least two provocative stimuli. Among these, arginine (ARG) has long been considered a classical, centrally mediated stimulus of GH secretion. ARG is also able to potentiate the GH response to GHRH, likely inhibiting hypothala-mic somatostatin; this combined test is one of the most potent to explore the maximal secretory capacity of somatotroph cells. Based on these premises, we verified whether the sequential administration of ARG and ARG+GHRH could be feasible as single step provocative test to evaluate the GH relea-sable pool in short children. To this goal, 48 normal short children (35 M and 13 F, 12.0±0.4 yr, PS 1: 255 II–IV: 23) underwent a test with ARG (0.5 g/kg iv from 0 to +30 min) followed by a coadmini-stration of ARG (from +120 to 150 min) plus GHRH (1 μg/kg iv at +120 min). ARG alone elicited a clear GH response (mean peak vs baseline: 12.1±1.7 vs 2.0±0.4 μg/l, p<0.001, Cmax range 12–51.0 μg/l). Following this GH rise, the hormonal levels at +120 min approached to baseline levels (4.2±0.8 μg/l) but then showed marked response to the coadmi-nistration of ARG+GHRH. The GH peak following ARG+GHRH (mean peak: 47.8±3.3 μg/l, p<0.001; Cmax 22.4–150.0 μg/l) was clearly higher (p<0.001) than that recorded after ARG alone. The GH responses to both ARG and ARG+GHRH were independent of gender, puberty, height velocity, body mass index (BMI) and IGF-I levels. Nine normal short children (16%) had GH peaks lower than 7 μg/l after ARG alone, while none showed GH peak below 20 μg/l after ARG+GHRH. Thus, ARG alone is a good stimulus of GH secretion but false positive responses frequently occur in normal short children. ARG+GHRH is a more potent stimulus giving no false positive responses even after previous challenge with ARG alone. Testing with sequential administration of ARG and ARG+GHRH may allow the single step evaluation of the somatotroph response to central and pituitary stimuli in short children.