Oral octreotide absorption in human subjects: comparable pharmacokinetics to parenteral octreotide and effective growth hormone suppression

CONTEXT

Oral administration of a novel octreotide formulation enabled its absorption to the systemic circulation, exhibiting blood concentrations comparable to those observed with injected octreotide and maintaining its biological activity.

OBJECTIVES

The aim of the study was to determine oral octreotide absorption and effects on pituitary GH secretion compared to sc octreotide injection.

DESIGN

Four single-dose studies were conducted in 75 healthy volunteers.

INTERVENTION

Oral doses of 3, 10, or 20 mg octreotide and a single sc injection of 100 μg octreotide were administered.

MAIN OUTCOME MEASURE

We measured the pharmacokinetic profile of orally administrated octreotide and the effect of octreotide on basal and stimulated GH secretion.

RESULTS

Both oral and sc treatments were well tolerated. Oral octreotide absorption to the circulation was apparent within 1 h after dose administration. Escalating oral octreotide doses resulted in dose-dependent increased plasma octreotide concentrations, with an observed rate of plasma decay similar to parenteral administration. Both 20 mg oral octreotide and injection of 0.1 mg sc octreotide resulted in equivalent pharmacokinetic parameters [mean peak plasma concentration, 3.77 ± 0.25 vs. 3.97 ± 0.19 ng/ml; mean area under the curve, 16.2 ± 1.25 vs. 12.1 ± 0.45 h × ng/ml); and median time ≥ 0.5 ng/ml, 7.67 vs. 5.88 h, respectively). A single dose of 20 mg oral octreotide resulted in basal (P < 0.05) and GHRH-stimulated (P < 0.001) mean GH levels suppressed by 49 and 80%, respectively.

CONCLUSIONS

The results support an oral octreotide alternative to parenteral octreotide treatment for patients with acromegaly.

Screening for primary aldosteronism in hypertensive subjects: results from two German epidemiological studies

OBJECTIVE

The prevalence of primary aldosteronism in unselected hypertensive patients is currently unknown. We investigated the frequency of positive screening results for primary aldosteronism based on the aldosterone-to-renin ratio (ARR) in hypertensive subjects aged 30-79 years from two German epidemiological studies. We further examined the frequency of positive screening results in subjects with resistant hypertension or stage III hypertension and assessed possible disparities between untreated and treated hypertensive subjects.

METHODS

Data were obtained from the first follow-ups of the population-based study of health in Pomerania (SHIP; n=1392) and the cooperative health research in the region of Augsburg (KORA; n=1052). Study-specific reference ranges for plasma aldosterone concentration (PAC), plasma renin concentration (PRC) and the ARR were applied. Confirmation tests for primary aldosteronism were not performed in these epidemiological studies.Three definitions for a positive screening for primary aldosteronism were applied: A) increased ARR; B) increased ARR and decreased PRC; and C) increased ARR and increased PAC and decreased PRC.

RESULTS

The frequency of positive screening results was 7.0, 3.8 and 0.2% according to definitions A-C respectively. In the subgroups of subjects with resistant hypertension (11.9, 5.5 and 0.9%) or stage III hypertension (18.3, 14.0 and 1.1%), these frequencies were markedly higher than those in the general hypertensive population. There was no difference in the frequency of positive screening results between the treated and untreated hypertensive subjects.

CONCLUSIONS

A maximum of 7.0% of the hypertensive population in Germany shows a positive screening result for primary aldosteronism. Thus, primary aldosteronism may be less frequent than previously expected based on data from referred hypertensive patients.

[Multimorbidity and successful aging: the population-based KORA-Age study]

BACKGROUND

The objective of the KORA-Age research consortium is to assess the determinants and consequences of multimorbidity in the elderly and to look into reasons for successful aging in the general public.

PATIENTS AND METHODS

In the KORA-Age cohort study 9,197 persons were included who where born in the year 1943 or before and participants of previous KORA cohort studies conducted between 1984 and 2001 (KORA: Cooperative Health Research in the Region of Augsburg). The randomized intervention study KORINNA (Coronary infarct follow-up treatment in the elderly) tested a nurse-based case management program with 338 patients with myocardial infarct and included an evaluation in health economics.

RESULTS

A total of 2,734 deaths were registered, 4,565 participants submitted a postal health status questionnaire and 4,127 participants were interviewed by telephone (response 76.2% and 68.9% respectively). A gender and age-stratified random sample of the cohort consisting of 1,079 persons took part in a physical examination (response 53.8%).

CONCLUSION

The KORA-Age consortium was able to collect data in a large population-based sample and is contributing to the understanding of multimorbidity and successful aging.

Effective combination treatment with cabergoline and low-dose pegvisomant in active acromegaly: a prospective clinical trial

CONTEXT

With adequate dose titration, pegvisomant normalizes IGF-I in up to 97% of patients with acromegaly. Pegvisomant is indicated for treatment-resistant disease but is expensive, particularly at a high dose. It has been used successfully in combination with somatostatin analogs. However, there are no therapeutic reports of pegvisomant in combination with dopamine agonists. Cabergoline is orally active, well-tolerated, and relatively inexpensive, and as monotherapy for acromegaly it is reported to normalize IGF-I in up to 30% of patients.

OBJECTIVE

The aim of the study was to investigate the efficacy of cabergoline monotherapy and pegvisomant in combination with cabergoline to control serum IGF-I in patients with active acromegaly. Twenty-four patients were recruited into a United Kingdom, multicenter, open-label, prospective clinical trial.

MAIN OUTCOME MEASURE

We measured the change in serum IGF-I.

RESULTS

After 18 wk of dose titration to a maximum dose of 0.5 mg once daily, cabergoline monotherapy did not significantly reduce IGF-I (454 ± 219 baseline vs. 389 ± 192 ng/ml cabergoline), although two patients did normalize IGF-I. The addition of 10 mg pegvisomant daily for 12 wk significantly reduced IGF-I (389 ± 192 ng/ml cabergoline vs. 229 ± 101 ng/ml combination), and 68% achieved a normal IGF-I. Twelve weeks after cabergoline withdrawal, while continuing to receive pegvisomant 10 mg, only 26% of patients maintained an IGF-I within the reference range (229 ± 101 ng/ml combination vs. 305 ± 177 ng/ml pegvisomant). There were no significant changes in liver transaminases or glucose metabolism throughout the study.

CONCLUSION

These data suggest that combination treatment with cabergoline and pegvisomant is more effective at reducing IGF-I levels than either cabergoline or pegvisomant monotherapy.

Association of IGF-I and the IGF-I/IGFBP-3 ratio with plasma aldosterone levels in the general population

Several studies in patients with acromegaly or growth hormone (GH) deficiency suggest a stimulatory effect of the growth hormone (GH)/insulin-like growth factor I (IGF-I) axis on the renin-angiotensin-aldosterone system (RAAS). We analyzed the association of serum IGF-I with plasma aldosterone and the aldosterone-to-renin ratio in a large sample from the general population. In addition to serum IGF-I levels, we also considered the IGF-I-to-IGF binding protein (IGFBP)-3 ratio. A total of 1 504 men and 1 566 women aged 25-88 were selected from the first follow-up of the population-based Study of Health in Pomerania. Plasma aldosterone and renin concentrations, as well as serum IGF-I and IGFBP-3 levels were determined with immunoassays. Analyses of variance and linear regression analyses were performed. We found positive associations between serum IGF-I or the IGF-I/IGFBP-3 ratio with plasma aldosterone in women but not in men. Plasma aldosterone levels increased by 2.91 ng/l per IGF-I standard deviation (SD) and by 2.17 ng/l per IGF-I/IGFBP-3 SD. The associations remained significant after exclusion of subjects taking RAAS-altering medication and of subjects with serum IGF-I levels and aldosterone-to-renin ratios outside the reference range. We conclude that, serum IGF-I and the IGF-I/IGFBP-3 ratio are associated with plasma aldosterone levels in women but not in men from the general population.

To live alone and to be depressed, an alarming combination for the renin-angiotensin-aldosterone-system (RAAS)

INTRODUCTION

The renin-angiotensin-aldosterone-system (RAAS) is one of the most important systems involved in the pathogenesis of cardiovascular diseases. Its role in stress response has been generally neglected, although the progression of cardiovascular disease is considerably increased in the presence of stress and especially in the presence of depression risk. With the present analysis we aimed to evaluate whether the activity of the RAAS correlates with depressive symptomatology and with chronic stress. Moreover, we aimed to analyse whether stress response is altered in the presence of depressed symptomatology. We chose "living alone" to be our paradigm of chronic stress.

METHODS AND RESULTS

Aldosterone and renin levels were assessed in 1743 (829 men, 914 women) from the population-based KORA study (Cooperative Health Research in the Region of Augsburg). The relationship between aldosterone, renin levels and the different combinations of living alone and depressive symptomatology was examined in three different multiple linear regression models adjusted for age, sex, creatinine levels, potassium levels, body mass index (BMI) and bio-behavioural factors. Neither "living alone" nor depressive symptomatology alone were associated with an activation of the RAAS, but the combination of living alone and depressive symptomatology yielded a highly significant increase in the aldosterone (p<0.01) and renin level (p=0.03).

CONCLUSION

Our findings show that depressive symptomatology is associated with a hyper-responsiveness to chronic stress. Under the condition of chronic stress depressed individuals have an activated RAAS. Activation of the RAAS might explain the known increased risk of negative cardiovascular disease outcomes in this group.

A case of an acromegalic patient resistant to the recommended maximum GH receptor antagonist dosage

BACKGROUND

The competitive GH receptor antagonist pegvisomant is reported to normalise IGF-1 levels in up to 97 % of acromegalic patients at a maximum dosage of 40 mg/d. Description of Case: We present an acromegalic patient resistant to the recommended maximum GH receptor antagonist dosage. The 60-year-old male patient presenting with typical clinical signs of acromegaly has underwent multiple transsphenoidal surgeries and pituitary irradiation, while currently available pharmacological therapies for acromegaly have been exhausted.

RESULTS

Biochemical control of the disease could only be achieved until uptitration of pegvisomant to 60 mg/d which was tolerated well.

CONCLUSIONS

The current treatment algorithm for acromegaly should be modified to treat cases of persistent and uncontrolled disease.

Effects on metabolic variables after 12-month treatment with a new once-a-week sustained-release recombinant growth hormone (GH: LB03002) in patients with GH deficiency

INTRODUCTION

GH substitution in GH deficiency (GHD) must be subcutaneously administered daily. A new sustained-release formulation of GH (LB03002) has been developed, which has to be injected once a week. As a substudy to the phase III study, we performed this prospective study to evaluate the influence of LB03002 on metabolic variables and hormones.

METHODS

Eleven patients with GHD [four women/seven men, 58 years (29-69 years)] without GH therapy were included in the study. Eight patients were treated with LB03002 for 12 months and three patients received placebo for 6 months followed by LB03002 for 6 months. A 3-h oral glucose tolerance test (OGTT) was performed at study entry and at study end. Additionally, IGF-I, cholesterol, LDL, HDL, triglycerides, leptin, ghrelin, HbA1c and C-peptide were measured. Body composition was evaluated by dual-energy X-ray absorptiometry (DXA), and waist/hip ratio (WHR) and waist/height (WHtR) ratio were measured by tape and scale.

RESULTS

Multiple of upper limit of normal (xULN) of IGF-I (0·23 (0·09-0·4) vs 0·71 (0·4-1·04), P < 0·01), WHR (0·98 (0·86-1·04) vs 1·01 (0·86-1·05), P < 0·05) and ghrelin levels [119·8 ng/l (67·7-266·6) vs 137 ng/l (67-289·5), P < 0·05] were significantly higher, whereas fat mass (FM) [34·7% (20·4-49·2) vs 32·4% (16·7-48·5), P < 0·05] and leptin [11·2 μg/l (3·3-55·7) vs 7·05 μg/l (2·4-54·3), P < 0·05] were significantly lower at study end. Glucose, insulin, HOMA-IR, ISI, HOMA-β, C-peptide and HbA1c during OGTT were not significantly different before and after GH substitution, neither were BMI, WHtR, bone mineral density and lipid variables.

CONCLUSION

Substitution with LB03002 showed statistically significant reduction in FM, which reduces leptin levels and increases ghrelin levels but does not seem to influence glucose and lipid metabolism.

Influence of pegvisomant on serum ghrelin and leptin levels in acromegalic patients

INTRODUCTION

Pegvisomant (peg) is a GH receptor antagonist. In de novo acromegalic patients with high GH levels, ghrelin and leptin levels are reduced, suggesting a direct GH-mediated effect. The aim of our study was to evaluate whether peg treatment in acromegalic patients may abolish the GH impact on ghrelin and leptin levels.

METHODS

Ghrelin, leptin and endogenous GH were measured in ten peg-treated acromegalic patients (three females/seven males, 47 years (28-57)), ten patients with active (act) and ten patients with inactive disease (inact) as well as in ten gender-, age- and body mass index (BMI)-matched healthy volunteers (controls). Endogenous GH was measured using a special in-house assay without interference by peg; total ghrelin and leptin were determined using a commercial RIA and an immunofluorometric in-house assay respectively.

RESULTS

Age and BMI did not differ significantly between groups. Endogenous GH was significantly higher in peg (6.3 μg/l (1.5-41)) and act (9.3 μg/l (1.7-70)) compared with controls (0.1 μg/l (0.1-3.1)) and inact (0.35 μg/l (0.1-2.0), P<0.001). Ghrelin was significantly higher in peg (232  ng/l (96-351)) compared with act (102 ng/l (33-232), P<0.01), whereas ghrelin was not significantly different between the other groups. Leptin was highest in controls (19 μg/l (4-57)) and lowest in act (6 μg/l (2-21)), but this difference did not reach significance.

CONCLUSION

Treatment with peg seems to disrupt the feedback loop of ghrelin and GH, leading to elevated ghrelin levels. Furthermore, peg therapy appears not to have a strong impact on leptin levels, as acromegalic patients with and without peg treatment showed similar leptin levels.

The acute effect of a single application of cabergoline on endogenous GH levels in patients with acromegaly on pegvisomant treatment

OBJECTIVE

Treatment with pegvisomant, an antagonist of growth hormone (GH) receptors, increases GH levels in a dose dependent manner. Cabergoline can suppress GH secretion in approximately 40% of acromegalic patients. However, the acute effects of cabergoline have not been studied in patients treated with pegvisomant. We performed this cross-sectional study to evaluate endogenous GH after an additional single cabergoline administration.

DESIGN

9 acromegalic patients on pegvisomant therapy were included. A 6h GH profile after pegvisomant alone (P) and a 9h profile in combination with oral cabergoline 0.5mg (PC) were performed. After 3 or 6h, all patients received a standardized light mixed meal. Endogenous serum GH and pegvisomant levels were measured by special in-house assays. The GH assay showed no interference with pegvisomant.

RESULTS

Endogenous GH levels at baseline did not differ significantly between the profiles (P: 16.5 μg/l (range 3.2-36.6 μg/l), PC: 8.0 μg/l (1.6-48 μg/l), p>0.05). In both profiles, GH fluctuated before meal. GH decreased more pronounced in PC but this decrease was not statistically significant. After meal, a significant decline in endogenous GH levels from 16.4 μg/l (0.4-27.1 μg/l, 100%) to 8.1 μg/l (0.2-24.7 μg/l, 66%) appeared in P at 300 min (p<0.01). Also in PC a decline from 7.8 μg/l (1.1-29.6 μg/l, 100%) to 5.2 μg/l (0.4-23.9 μg/l, 75%) at 300 min was observed but it was not significant.

CONCLUSION

Endogenous GH is not significantly decreased after a single oral cabergoline application during pegvisomant treatment in acromegaly.

Is primary aldosteronism associated with diabetes mellitus? Results of the German Conn's Registry

Aldosterone excess in the context of primary aldosteronism (PA) has been associated with impaired glucose tolerance and diabetes mellitus. We retrospectively assessed the prevalence of diabetes mellitus in patients from the German Conn's Register and compared the data with those from hypertensive subjects of a population-based survey. In a case-control study, we have compared 638 patients with PA from the German Conn's registry who were treated in 6 German centers with 897 hypertensive control subjects from the population-based F3 survey of the Cooperative Health Research in the Region of Augsburg (KORA). The samples were matched for age, sex, and blood pressure in a 1:1 ratio. Risk factors associated with the presence of diabetes mellitus were calculated in 638 patients with PA and 897 hypertensive controls. In the case control study, the diabetes prevalence was calculated in 338 cases and controls. In patients with primary aldosteronism, age, BMI, and a higher number of antihypertensive drugs (lowest tertile vs. highest tertile) were variables associated with diabetes mellitus. In contrast, serum potassium and plasma aldosterone concentrations were not associated with higher diabetes prevalence, whereas diastolic blood pressure was inversely associated with diabetes mellitus. Diabetes mellitus was more prevalent in patients with PA than in 338 matched controls (23 vs. 10% in controls). Our data for the German population show that diabetes mellitus is more prevalent in patients with primary aldosteronism than in hypertensive controls.

Salivary aldosterone as a diagnostic aid in primary aldosteronism

Recent evidence demonstrates an increased incidence of primary aldosteronism (PA) in approximately 10% of the hypertensive population, making noninvasive and simple screening methods necessary. The aim of the present study was to apply a time-resolved fluorescence immunoassay for the measurement of aldosterone in saliva and the establishment of a cut-off to identify patients with a high likelihood for PA requiring subsequent screening with the aldosterone to renin ratio. Saliva was collected (AM and PM) to ascertain an optimum time with best discriminating power between healthy and disease states. Plasma aldosterone, after overnight recumbency and 4 h later, was collected for posture testing. The participants included 53 PA patients (aged 14-78), 54 with essential hypertension (EH, aged 19-82), and 38 healthy volunteers (aged 19-56). Saliva aldosterone (SA) (median, 25-75(th)%) in PA was found at 90 pg/ml (61-139) compared to 53 pg/ml (40-85) in EH, with discrimination between PA versus EHs best in the morning (cutoff: 81 pg/ml, 77% sensitivity, 82% specificity). Saliva aldosterone decreases throughout the day in patients with adenomas [APA AM: 123 pg/ml (92-213) vs. PM: 79 pg/ml (41-116)], but not in those with bilateral hyperplasia [BAH AM: 85 pg/ml (59-115)] vs. pm 69 pg/ml (57-114). Morning SA alone allows discrimination between PA and controls, though with significant overlap against EHs, leading to a high number of false positives. More promising is the use of diurnal variation in SA in distinguishing between APA and BAH. The decline in SA seen in patients with APA presents a more constant finding compared to posture testing, which fails to correctly classify a large number of patients.

Endogenous estradiol may influence IGF-I levels in acromegalic women treated with pegvisomant

We present the case of a 46-year-old woman with acromegaly currently being treated with the growth hormone (GH) receptor antagonist pegvisomant showing strongly fluctuating IGF-I levels. We prospectively measured estradiol, IGF-I, IGF-I binding protein, acid labile subunit, basal endogenous GH, binding protein and pegvisomant levels for 6 months every week. Estradiol levels showed a strongly negative correlation with IGF-I (r = -0.733, P < 0.001), and less so with ALS (r = -0.433, P < 0.05) and IGFBP3 (r = -0.590, P < 0.01). Estradiol was not significantly correlated with endogenous GH or pegvisomant levels. Likewise, IGF-I did not correlate with endogenous GH or pegvisomant levels. In our patient, endogenous estradiol levels have a significant influence on IGF-I levels. When female acromegalic patients on permanent pegvisomant treatment show fluctuating IGF-I levels, estradiol levels should be taken into consideration.

Saliva as a medium for aldosterone measurement in repeated sampling studies

BACKGROUND

Saliva is a readily available biological fluid, making it convenient in diagnosis of diseases and in multi-sampling protocols. Several salivary steroids give a useful index of free plasma levels. Increased incidence of primary aldosteronism (PA) in approximately 10% of the hypertensive population has increased interest in the mineralocorticoid aldosterone.

METHODS

A biotinylated-aldosterone tracer and a commercially available antibody are used in a time-resolved fluorescence immunoassay (TR-FIA) to measure salivary aldosterone (SA). Saliva was collected in various multi-sampling protocols: Investigation of diurnal rhythm in healthy and PA patients, ACTH stimulation test and posture test in healthy subjects.

RESULTS

Method validation showed a sensitivity of 19 ng/L and intra-/inter-assay precision between 7.2-10.1% and 8.7-15.7%, respectively. SA correlated significantly (y = 0.2995x +/- 0.01, r(2)=0.60) to plasma aldosterone measured by a commercial radioimmunoassay. SA (median; 95%CI) was at 111 (95-127)ng/L in PA (n=84) and 50 (44-56)ng/L in healthy subjects (n=60). After change in posture, aldosterone increased in both, saliva (57 (47-63)ng/L to 95 (84-117)ng/L) and plasma (26 (26-41)ng/L to 135 (110-181)ng/L). Peak levels were reached after 1h, and were higher in females than in males.

CONCLUSIONS

SA correlates well to plasma aldosterone and mirrors responses during conditions of stress. SA is significantly higher in PA, and the diurnal rhythm seen in the healthy is blunted in PA. We additionally found gender-dependent differential responses to posture, with higher increases in females. Measurement of aldosterone in saliva presents a useful and convenient method for application in multi-sampling studies.