A randomized study of SMS 201-995 versus bromocriptine treatment in acromegaly: clinical and biochemical effects

Surgical and non-surgical interventions for primary and salvage treatment of growth hormone-secreting pituitary adenomas in adults

BACKGROUND

Growth hormone (GH)-secreting pituitary adenoma is a severe endocrine disease. Surgery is the currently recommended primary therapy for patients with GH-secreting tumours. However, non-surgical therapy (pharmacological therapy and radiation therapy) may be performed as primary therapy or may improve surgical outcomes.

OBJECTIVES

To assess the effects of surgical and non-surgical interventions for primary and salvage treatment of GH-secreting pituitary adenomas in adults.

SEARCH METHODS

We searched CENTRAL, MEDLINE, WHO ICTRP, and ClinicalTrials.gov. The date of the last search of all databases was 1 August 2022. We did not apply any language restrictions.

SELECTION CRITERIA

Randomised controlled trials (RCTs) and quasi-RCTs of more than 12 weeks' duration, reporting on surgical, pharmacological, radiation, and combination interventions for GH-secreting pituitary adenomas in any healthcare setting.

DATA COLLECTION AND ANALYSIS

Two review authors independently screened titles and abstracts for relevance, screened for inclusion, completed data extraction, and performed a risk of bias assessment. We assessed studies for overall certainty of the evidence using GRADE. We estimated treatment effects using random-effects meta-analysis. We expressed results as risk ratios (RR) for dichotomous outcomes together with 95% confidence intervals (CI) or mean differences (MD) for continuous outcomes, or in descriptive format when meta-analysis was not possible.

MAIN RESULTS

We included eight RCTs that evaluated 445 adults with GH-secreting pituitary adenomas. Four studies reported that they included participants with macroadenomas, one study included a small number of participants with microadenomas. The remaining studies did not specify tumour subtypes. Studies evaluated surgical therapy alone, pharmacological therapy alone, or combination surgical and pharmacological therapy. Methodological quality varied, with many studies providing insufficient information to compare treatment strategies or accurately judge the risk of bias. We identified two main comparisons, surgery alone versus pharmacological therapy alone, and surgery alone versus pharmacological therapy and surgery combined. Surgical therapy alone versus pharmacological therapy alone Three studies with a total of 164 randomised participants investigated this comparison. Only one study narratively described hyperglycaemia as a disease-related complication. All three studies reported adverse events, yet only one study reported numbers separately for the intervention arms; none of the 11 participants were observed to develop gallbladder stones or sludge on ultrasonography following surgery, while five of 11 participants experienced any biliary problems following pharmacological therapy (RR 0.09, 95% CI 0.01 to 1.47; 1 study, 22 participants; very low-certainty evidence). Health-related quality of life was reported to improve similarly in both intervention arms during follow-up. Surgery alone compared to pharmacological therapy alone may slightly increase the biochemical remission rate from 12 weeks to one year after intervention, but the evidence is very uncertain; 36/78 participants in the surgery-alone group versus 15/66 in the pharmacological therapy group showed biochemical remission. The need for additional surgery or non-surgical therapy for recurrent or persistent disease was described for single study arms only. Surgical therapy alone versus preoperative pharmacological therapy and surgery Five studies with a total of 281 randomised participants provided data for this comparison. Preoperative pharmacological therapy and surgery may have little to no effect on the disease-related complication of a difficult intubation (requiring postponement of surgery) compared to surgery alone, but the evidence is very uncertain (RR 2.00, 95% CI 0.19 to 21.34; 1 study, 98 participants; very low-certainty evidence). Surgery alone may have little to no effect on (transient and persistent) adverse events when compared to preoperative pharmacological therapy and surgery, but again, the evidence is very uncertain (RR 1.23, 95% CI 0.75 to 2.03; 5 studies, 267 participants; very low-certainty evidence). Concerning biochemical remission, surgery alone compared to preoperative pharmacological therapy and surgery may not increase remission rates up until 16 weeks after surgery; 23 of 134 participants in the surgery-alone group versus 51 of 133 in the preoperative pharmacological therapy and surgery group showed biochemical remission. Furthermore, the very low-certainty evidence did not suggest benefit or detriment of preoperative pharmacological therapy and surgery compared to surgery alone for the outcomes 'requiring additional surgery' (RR 0.48, 95% CI 0.05 to 5.06; 1 study, 61 participants; very low-certainty evidence) or 'non-surgical therapy for recurrent or persistent disease' (RR 1.22, 95% CI 0.65 to 2.28; 2 studies, 100 participants; very low-certainty evidence). None of the included studies measured health-related quality of life. None of the eight included studies measured disease recurrence or socioeconomic effects. While three of the eight studies reported no deaths to have occurred, one study mentioned that overall, two participants had died within five years of the start of the study.

AUTHORS' CONCLUSIONS

Within the context of GH-secreting pituitary adenomas, patient-relevant outcomes, such as disease-related complications, adverse events and disease recurrence were not, or only sparsely, reported. When reported, we found that surgery may have little or no effect on the outcomes compared to the comparator treatment. The current evidence is limited by the small number of included studies, as well as the unclear risk of bias in most studies. The high uncertainty of evidence significantly limits the applicability of our findings to clinical practice. Detailed reporting on the burden of recurrent disease is an important knowledge gap to be evaluated in future research studies. It is also crucial that future studies in this area are designed to report on outcomes by tumour subtype (that is, macroadenomas versus microadenomas) so that future subgroup analyses can be conducted. More rigorous and larger studies, powered to address these research questions, are required to assess the merits of neoadjuvant pharmacological therapy or first-line pharmacotherapy.

Medical Treatments for Acromegaly: A Systematic Review and Network Meta-Analysis

BACKGROUND

Acromegaly results from the hypersecretion of growth hormone. Because of the low incidence rates of this disease worldwide, few clinical trials evaluating drug treatments have been conducted.

OBJECTIVES

To conduct the first network meta-analysis simultaneously comparing all available drugs used in acromegaly treatment so as to provide more robust evidence in this field.

METHODS

A systematic review was performed according to Preferred Reporting Items for Systematic Reviews and Meta-Analyses and Cochrane Collaboration recommendations (PROSPERO database under the registration number CRD42017059880). The electronic searches were conducted in PubMed (MEDLINE), Scopus, and Web of Science databases. Randomized controlled trials comparing any drug for the treatment of acromegaly head-to-head or versus placebo were included. Outcomes concerning the efficacy and safety of treatments were evaluated. The statistical analyses were performed using Aggregate Data Drug Information System version 1.16.8 (drugis.org, Groningen, The Netherlands).

RESULTS

The initial search retrieved 2059 articles. Of these, 10 randomized controlled trials were included in a qualitative analysis and 7 in a quantitative analysis. The network meta-analysis for the efficacy outcome (number of patients achieving insulinlike growth factor 1 control) showed that pegvisomant and lanreotide autogel were statistically superior to placebo (odds ratio [95% credible interval] 0.06 [0.00-0.55] and 0.09 [0.01-0.88]). No further differences were found. The probability rank indicated that pegvisomant and pasireotide have the highest probabilities (33% and 34%, respectively) of being the best therapeutic options. No major side effects were noted.

CONCLUSIONS

Pegvisomant is still a good option for acromegaly treatment, but pasireotide seems to be a promising alternative. Nevertheless, other important key factors such as drug costs and effectiveness (real-world results) should be taken into account when selecting acromegaly treatment.

Effects of somatostatin analogs on glucose homeostasis: a metaanalysis of acromegaly studies

BACKGROUND

Somatostatin analogs (SSA) may influence glucose metabolism, but the clinical relevance of this effect is uncertain because trials performed so far are limited in terms of number of patients and heterogeneity for length and type of follow-up.

PURPOSE

The purpose of the study was to assess, via the metaanalysis of acromegaly studies, the clinical impact of SSA on glucose metabolism. The outcomes analyzed were fasting plasma glucose, fasting plasma insulin, hemoglobin A(1c), and plasma glucose concentrations during oral glucose tolerance test.

STUDY SELECTION

Eligibility criteria were: 1) duration of SSA treatment of at least 3 wk; 2) available numerical data for at least one of the four biochemical outcomes investigated; 3) measurement of the outcomes before and after SSA treatment; and 4) no selection of acromegalic patients for their responsivity to SSA. After revision, only 31 studies fulfilled eligibility criteria and were therefore selected for data extraction and analysis.

DATA SYNTHESIS

SSA treatment was found to induce statistically significant decrease in fasting plasma insulin [effect size -0.45, 95% confidence interval (CI) from -0.58 to -0.32, P < 0.001], without any significant change of fasting plasma glucose (effect size +0.04, 95% CI from -0.07 to +0.15, P = 0.52) and hemoglobin A(1c) (effect size +0.11, 95% CI from -0.02 to +0.23, P = 0.09). Serum glucose values during the oral glucose tolerance test were shown to significantly change during SSA treatment (effect size +0.31, 95% CI from +0.17 to +0.45, P < 0.001), although with high inconsistency among trials.

CONCLUSIONS

Our data suggest that modifications of glucose homeostasis induced by SSA may have an overall minor clinical impact in acromegaly.

A critical analysis of pituitary tumor shrinkage during primary medical therapy in acromegaly

CONTEXT

Somatostatin analogs have been successfully used to treat patients with GH-secreting pituitary adenomas because they are safe, effective, and usually well tolerated. The results of studies evaluating acromegaly treatment with the somatostatin receptor ligands (SRLs), octreotide and lanreotide, have supported the use of these agents for primary medical therapy before or as an alternative to traditional interventions of surgery and radiotherapy in selected cases.

EVIDENCE ACQUISITION

We therefore undertook a systematic literature overview to characterize the results of studies involving primary therapy with somatostatin analogs and their effects on pituitary tumor size. Because most studies in which pituitary tumor shrinkage has been assessed involve uncontrolled, open-label, prospective trials or retrospective case series, the lack of a control arm does not permit pooling of data in a metaanalytic fashion to determine tumor size reduction. Therefore, this systematic review was designed to document and stratify data by study design, summarize therapeutic regimens and patient characteristics, assess the percentage of patients showing changes in tumor size, and calculate the weighted average effect on size reduction.

EVIDENCE SYNTHESIS

Overall, for patients who experience significant shrinkage, an approximately 50% decrease in pituitary mass is achieved when a somatostatin analog is used exclusively or before surgery or radiotherapy. Fourteen studies (n = 424) provided a definition of significant tumor shrinkage, and the results showed that 36.6% (weighted mean percentage) of patients receiving primary SRL therapy for acromegaly experienced a significant reduction in tumor size. The weighted mean percent reduction in tumor size was 19.4% for those studies in which all patients received SRLs and change in tumor size was reported for all patients.

CONCLUSIONS

Clinical implications are discussed for patients in whom tumor size control with SRLs is an important objective, typically those who have failed surgery or are being treated with primary medical therapy with large tumors.

Thyrotrophin-releasing hormone receptor 1 and prothyrotrophin-releasing hormone mRNA expression in the central nervous system are regulated by suckling in lactating rats

BACKGROUND

The accepted function of the hypothalamic peptide, thyrotrophin-releasing hormone (TRH), is to initiate release of thyrotrophin (TSH) from the pituitary. A physiological role for TRH in lactating rats has not yet been established.

METHODS

Tissues were prepared from random-cycling and lactating rats and analysed using Northern blot, real time RT-PCR and quantitative in situ hybridisation.

RESULTS

This study demonstrates that TRH receptor 1 (TRHR1) mRNA expression is up-regulated in the pituitary and in discrete nuclei of the hypothalamus in lactating rats, while proTRH mRNA expression levels are increased only in the hypothalamus. The results were corroborated by quantitative in situ analysis of proTRH and TRHR1. Bromocriptine, which reduced prolactin (PRL) concentrations in plasma of lactating and nursing rats, also counteracted the suckling-induced increase in TRHR1 mRNA expression in the hypothalamus, but had an opposite effect in the pituitary. These changes were confined to the hypothalamus and the amygdala in the brain.

CONCLUSIONS

The present study shows that the mechanisms of suckling-induced lactation involve region-specific regulation of TRHR1 and proTRH mRNAs in the central nervous system notably at the hypothalamic level. The results demonstrate that continued suckling is critical to maintain plasma prolactin (PRL) levels as well as proTRH and TRHR1 mRNA expression in the hypothalamus. Increased plasma PRL levels may have a positive modulatory role on the proTRH/TRHR1 system during suckling.

Effectiveness of secondary transnasal surgery in GH-secreting pituitary macroadenomas

Transsphenoidal surgery is the first therapeutic option in acromegaly, but the management of persistent or recurrent cases of the disease after surgery has been controversial. This study presented the results of secondary transnasal surgery for residual or recurring growth hormone (GH)-secreting macroadenoma with reference to intraoperative GH measurement. It focused on 22 patients who underwent secondary transsphenoidal surgery for 18 residual and 4 recurring GH-secreting pituitary macroadenomas from 1990 to 1999. To assess complete tumor removal, plasma GH concentration was measured intraoperatively. Before secondary surgery, plasma GH levels without medical treatment ranged from 2.0 to 239.0 microg/l (mean 31.5 +/- 50.4). Magnetic resonance imaging demonstrated 16 transnasally resectable tumors and 6 nonresectable grossly invasive tumors. Intraoperative plasma GH concentrations declined sufficiently in 9 of 16 with transnasally resectable tumors, but in the remaining 7 cases the tumors were further explored and normalization of GH levels was ultimately obtained in 4 out of these cases. It was impossible to completely remove the tumors in all the 6 patients with transnasally nonresectable tumors. Thirteen of 22 patients achieved endocrinological remission by rigorous criteria. In transnasally resectable tumors, the endocrinological remission rate was 81.3% (13 of 16 patients) with no recurrence during the follow-up period of at least 4 years. Secondary transnasal surgery for residual or recurring GH-secreting pituitary macroadenomas is a safe and effective treatment, if done along with intraoperative GH measurement. Endocrinological remission can be obtained with high probability in patients who suffer from macroadenomas with suprasellar extension, with the exception of transnasally nonresectable grossly invasive tumors.

Anti-proliferative effects and cell death mediated by two isoforms of dopamine D2 receptors in pituitary tumor cells

Stable rat pituitary tumor cell lines expressing two isoforms of the dopamine D2 receptor, D2L (long) and D2S (short) (the GH3D2L and GH3D2S cell lines, respectively), were established, and the signaling pathway underlying the anti-proliferative and cell death effects of dopaminergic agonists was examined in these cells. After either dopamine or quinpirole treatment, the cell viability decreased significantly only in GH3D2L cells and GH3D2S cells, but not in GH3 cells where D2 receptors are absent. Treatment with haloperidol, a specific D2 receptor antagonist, rescued the dopamine-mediated decreased cell viability in both the GH3D2L and GH3D2S cells. Treatment of these cells with dopamine decreased the DNA synthesis rate, as demonstrated by the incorporation of 5-bromo-2'-deoxyuridine (BrdU). Dopamine-induced cell death was observed in the GH3D2L and GH3D2S cells, and was accompanied by DNA laddering and caspase-3 activation, which were blunted by haloperidol, indicating that dopamine-induced cell death in these cells is mediated by the dopamine D2 receptors. D2 receptor-mediated cell death in these cells correlated with the sustained and enhanced activation of p38 mitogen-activated protein kinase (MAPK) and the extracellular-signal regulated kinase (ERK)1/2 pathways. Treatment with SB203580, which is a specific p38 MAPK inhibitor and PD98059, which is an inhibitor of MEK1/ERK signaling, selectively abrogates dopamine-induced cell death. It was further shown that p38 MAPK and ERK activation was inhibited by the antioxidant, N-acetylcysteine (NAC), and that a treatment with haloperidol completely blocked the p38 and ERK activation induced by dopamine. These results suggest that dopamine induces an anti-proliferative effect and cell death via the dopamine D2 receptors, by means of the p38 MAPK and ERK pathways involving oxidative stress, in the pituitary tumor cells.

Demonstration of enhanced potency of a chimeric somatostatin-dopamine molecule, BIM-23A387, in suppressing growth hormone and prolactin secretion from human pituitary somatotroph adenoma cells

In acromegaly, the combination of somatostatin (SS) and dopamine (DA) agonists has been shown to enhance suppression of GH secretion. In the present study, a new chimeric molecule, BIM-23A387, which selectively binds to the SS subtype 2 receptor (sst(2); K(i) = 0.10 nM) and to the DA D2 receptor (D2DR; K(i) = 22.1 nM) was tested in cultures prepared from 11 human GH-secreting tumors for its ability to suppress GH and prolactin (PRL) secretion. The chimeric compound was compared with individual sst(2) and D2DR agonists of comparable activity at the individual receptors. All tumors expressed both sst(2) and D2DR mRNAs (0.8 +/- 0.2 and 4.7 +/- 0.7 copy/copy beta-glucuronidase mRNA, respectively). In cell cultures from seven octreotide-sensitive tumors, the maximal inhibition of GH release induced by the individual sst(2) and D2DR analogs and by BIM-23A387 was similar. However, the mean EC(50) for GH suppression by BIM-23A387 (0.2 pM) was 50 times lower than that of the individual sst(2) and D2DR analogs, either used individually or combined. Similar data were obtained in four tumors that were only partially responsive to octreotide. The inhibition of GH release by BIM-23A387 was only partially reversed by the D2R2 antagonist, sulpiride, or by the sst(2) antagonist, BIM-23454. Only when both antagonists were combined was the GH suppressive effect of BIM-23A387 totally reversed. Finally, BIM-23A387 produced a mean 73 +/- 6% inhibition of PRL in six mixed GH plus PRL tumors. These data demonstrate an enhanced potency of the chimeric molecule, BIM-23A387, in suppressing GH and PRL secretion from acromegalic tumors, which cannot be explained merely on the basis of binding affinity for SS and/or DA receptors.

Growth hormone receptor antagonists: discovery, development, and use in patients with acromegaly

An understanding of the events that occur during GH receptor (GHR) signaling has facilitated the development of a GHR antagonist (pegvisomant) for use in humans. This molecule has been designed to compete with native GH for the GHR and to prevent its proper or functional dimerization-a process that is critical for GH signal transduction and IGF-I synthesis and secretion. Clinical trials in patients with acromegaly show GHR blockade to be an exciting new mode of therapy for this condition, and pegvisomant may have a therapeutic role in diseases, such as diabetes and malignancy, in which abnormalities of the GH/IGF-I axis have been observed. This review charts the discovery and development of GHR antagonists and details the experience gained in patients with acromegaly.

Current status and future opportunities for controlling acromegaly

Growth-hormone (GH) secreting adenomas, including acromegaly, account for approximately one-sixth of all pituitary adenomas and are associated with mortality rates at least twice that of the general population. The ultimate goal of therapy for acromegaly is normalization of morbidity and mortality rates achieved through removal or reduction of the tumor mass and normalization of insulin-like growth factor I (IGF-I) levels. Previously published efficacy results of current treatment modalities (surgery, conventional radiation, and medical therapy with dopamine agonists and somatostatin analogs) are often difficult to compare because of the different criteria used to define cure (some of which are now considered inadequate). For each of these modalities, pooled data from a series of acromegaly studies were reviewed for rates of IGF-I normalization, a currently accepted definition of cure. The results showed overall cure rates of approximately 10% for bromocriptine, 34% for cabergoline, 36% for conventional radiation, 50-90% for surgery for microadenomas and less than 50% for macroadenomas, and 54-66% for octreotide. These cure rates based on IGF-I normalization are generally less than those reported for cure based solely on GH levels. Novel new therapies for acromegaly include the somatostatin analog, lanreotide, Gamma Knife radiosurgery, and pegvisomant, the first in its class of new GH receptor antagonists. Although it does not appear that Gamma Knife radiosurgery results in significantly higher cure rates or fewer complications, it does provide a notable improvement in delivery compared with conventional radiation. Early studies have reported IGF-I normalization in 48% of lanreotide-treated patients and up to 97% of pegvisomant-treated.

In vivo and in vitro effects of octreotide, quinagolide and cabergoline in four hyperprolactinaemic acromegalics: correlation with somatostatin and dopamine D2 receptor scintigraphy

OBJECTIVE

GH and PRL cosecretion frequently occurs in acromegaly and the sensitivity of both hormones to somatostatin analogs (SA) and dopamine agonists (DA) alone or in combination, is still debated. This study was designed to evaluate the in vivo and in vitro sensitivity to SA and/or DA and correlate the response in terms of hormone suppression to the results of in vivo somatostatin and dopamine receptor scintigraphy and to the immunohistochemical findings.

DESIGN AND PATIENTS

Scintigraphy using 111In-DTPA-D-Phe(1)-OCT (111In-OCT) and 123I-methoxybenzamide (123I-IBZM) was performed in four patients with acromegaly and high circulating GH, PRL and IGF-I levels. The results were correlated with the response to long-term treatment with octreotide (OCT), quinagolide (QN) and/or cabergoline (CAB), to the in vitro hormone suppression by OCT and DA in primary cultures from the pituitary tumors and to the immunohistochemical findings.

RESULTS

The first patient showed high tumour uptake of 111In-OCT and 123I-IBZM, the second high uptake of only 111In-OCT, while the third one showed faint tumour uptake of only 123I-IBZM, and the fourth a faint uptake of 111In-OCT. In the first and in the fourth patients OCT or CAB administered alone failed to normalize hormone levels while the combined treatment induced circulating GH, IGF-I and PRL normalization. In the second patient OCT administered alone normalized hormone levels while QN reduced PRL levels only. In the third patient both OCT and QN, alone or in combination, failed to normalize hormone levels. However, in this patient GH and PRL suppression was significantly greater after QN than OCT treatment. After medical therapy, all the patients were operated on. Immunohistochemistry showed diffuse GH and focal PRL staining in the first patient, while diffuse GH and PRL staining in the remaining three. In vitro, OCT significantly suppressed GH secretion in the four primary pituitary tumor cultures, while PRL secretion was significantly suppressed only in the second and the fourth cases. Dopamine agonists (DA) significantly suppressed PRL release in all the cultures, while GH secretion was significantly suppressed in three out of four.

CONCLUSIONS

These four acromegalics, presenting similar clinical findings and comparable peripheral hormone levels, showed different responsiveness to SA and DA. Moreover, during the in vitro study on primary tumor cell cultures, OCT and DA displayed an inhibiting activity on GH and PRL secretion positively correlated with the response observed in vivo. This evidence together with the in vivo receptor imaging study suggest the existence of somatostatin and/or dopamine D2 receptor heterogeneity in this class of pituitary tumors. The new potent DA might be primarily considered in the medical treatment of hyperprolactinemic acromegalics, while SA alone or in combination with DA in case of ineffective hormone suppression.

Treatment of Chinese acromegaly with a combination of bromocriptine and octreotide

BACKGROUND

Good results have been reported with combined use of octreotide and bromocriptine in acromegalic Caucasians. Data concerning the efficacy and tolerability of this combination treatment in Chinese acromegalic patients are scanty.

AIM

The aim of this study was to assess the efficacy and tolerability of combined therapy using bromocriptine and octreotide in the treatment of acromegaly in Chinese patients and to compare the cost-effectiveness of various regimes.

METHODS

Sixteen Chinese acromegalic patients with growth hormone (GH) concentration not suppressible to below 5 mU/L (2 microg/L) during an extended OGTT were recruited to undergo four phases of the study. During the study period, the patients were given bromocriptine alone, bromocriptine and low dose octreotide, bromocriptine and medium dose octreotide, and medium dose octreotide alone. Plasma concentrations of GH and insulin-like growth factor-1 (IGF-1) were measured before and after the completion of each phase.

RESULTS

The number of patients reaching target GH concentrations was significantly higher when treated with octreotide compared to baseline (p<0.05). Bromocriptine alone had a significant effect but not to the extent of octreotide alone. A combination of low dose octreotide and bromocriptine is as efficacious in the treatment of acromegaly as high dose octreotide. None of the patients suffered from serious adverse effects.

CONCLUSION

The results confirmed the usefulness and tolerability of bromocriptine and octreotide in Chinese acromegalics. The most cost-effective regime in this study was a combination of low dose octreotide and bromocriptine.

Medical therapy for acromegaly

Both somatostatin analogues, which bind to the somatostatin receptor subtypes 2 and 5, and dopamine agonists, which are specific for the D2 receptor, have been used to treat acromegaly. Each of these classes of drugs contains several compounds that vary in duration of action, efficacy, and side effect profile. Although somatostatin analogues reduce GH levels and alleviate symptoms in most patients and restore IGF-1 levels to normal in 60% to 65% of patients, tumor shrinkage is limited to 40% of patients. evidence in the literature supports the use of these medications as secondary therapy in patients with acromegaly who have had surgery and who continue to have elevated GH levels (above 2 ng/mL during an oral glucose tolerance test) with or without IGF-1 concentrations that are above the upper limit of normal for age. In addition, medical therapy indicated in patients who refuse surgery and in patients who are poor surgical candidates. The controversial question is whether medical therapy should be an option for primary treatment of the acromegalic patient. Currently, ther are no data from prospective randomized trials comparing the effects of surgery versus somatostatin analogues as first-line therapy for for newly diagnosed acromegalic patients. Limited data from nonrandomized studies demonstrate that somatostatin analogues are effective long-term in suppressing GH and reducing IGF-1 into the normal range in approximately two-thirds of patients who have never undergone previous treatment. It is still the consensus that patients with GH-secreting microadenomas should undergo surgical resection, because the likelihood of complete cure by an experience neurosurgeon is high, at least 70% or greater. Successful surgical treatment has the advantage of completely removing the tumor in contrast to medical therapy, which rarely produces shrinkage greater than 50% despite the fact that IGF-1 and GH levels may be normal. In patients with macroadenomas of a size and location that suggest that the chance of complete resection is 40% or less, primary treatment with a somatostatin analogue should be considered as one option in the initial management of the patient. Another option in such an individual would be surgical debulking followed by medical therapy, because it is theoretically possible that biochemical cure with medical therapy after surgical debulking might be achieved with lower doses. The cost-effectiveness of these approaches has not yet been determined. Once the decision has been made to begin medical therapy, a choice must be made between dopamine agonists and somatostatin analogues. Most evidence suggests that somatostatin analogues are more effective than dopamine agonists and therefore would be the therapy of choice. In select patients, dopamine agonists, particularly the long-acting agonist cabergoline, may be preferred initially if the patient is unwilling to take injections or if the GH elevations are relatively modest (< 10 ng/mL). Biochemical cure should be assessed by measurement of GH (which can be performed 2 hours after an octreotide injection) and IGF-1 concentrations. The goal of treatment include reduction of of GH below 2 ng/mL and reduction of IGF-1 into the normal range. In patients who do not reach these goals, the dose or frequency of injection of the somatostatin analogue or both should be increased. If such measures are unsuccessful, a dopamine agonist may be added to the medical regimen because some studies suggest that combination therapy may be more effective in select cases than octreotide therapy alone. If such measures are still unsuccessful, other options should be considered, including surgery, pituitary radiation, and medical treatment with investigational drugs.

Lack of effect of the dopamine D1 antagonist, NNC 01-0687, on unstimulated and stimulated release of anterior pituitary hormones in males

Dopamine in humans inhibits the secretion of luteinizing hormone (LH), follicular stimulating hormone (FSH), thyroid stimulating hormone (TSH) and prolactin (PRL), and is a stimulator of growth hormone (GH) secretion. Dopamine-D1 receptor stimulation with fenoldopam increases basal PRL levels, suppresses TSH, and increases gonadotropin releasing hormone (LHRH) induced LH release. We have investigated the effect of a dopamine D1-receptor antagonist, NNC 01-0687, on the secretion of anterior pituitary hormones. In 8 healthy males NNC 01-0687 and placebo were administered orally in a double-blind placebo controlled cross-over study for three days with a wash-out period of 14 days. Hormonal responses (PRL, LH, FSH, GH, TSH, thyroid hormones and testosterone), unstimulated and LHRH/TRH stimulated, were studied on days 1 and 3. No significant difference (p > 0.05) between placebo and active periods was found neither in unstimulated nor in stimulated hormone concentrations expressed in absolute values, percent change of before, incremental values and area under the curve. These results suggest that the neuronal DA-D1 activity is not activated during basal conditions in healthy male subjects.

Heterogeneous dopamine D2 receptor subtype messenger ribonucleic acid expression in clinically nonfunctioning pituitary adenomas

Little is known about differences in the expression, localization, and function of the two dopamine D2 receptor subtypes, D2short and D2long (D2s and D2l), in either normal or adenomatous pituitary. We investigated the messenger RNA (mRNA) expression of the D2 receptor (D2R) subtypes in clinically nonfunctioning pituitary adenomas by in situ hybridization using subtype-specific oligonucleotides. The five normal pituitaries studied expressed similar ratios of D2R subtypes mRNA with a predominant expression of the D2l isoform. In 2 of 18 clinically inactive adenomas no D2R mRNA was found, whereas in 16 a heterogeneous expression of D2R isoforms was observed. Six adenomas expressed only the D2l and 2 adenomas only the D2s subtype mRNA; the remaining 8 expressed extremely varying proportions of the two subtypes. The D2R was found only in a subset of the nonfunctioning adenoma cells. In gonadotropin-immunopositive adenomas, the D2R was mainly localized in LH- and FSH-immunopositive cells. Probably because of the heterogeneous D2R subtype expression, suppression of cell proliferation was observed in only 3 of 9 adenoma cell cultures in which the growth inhibitory effect of bromocriptine was studied. Although there is some evidence that the presence of the D2s receptor subtype favors the growth inhibitory response to bromocriptine, further studies with a larger number of inactive adenomas are needed to confirm this speculation.

Cabergoline in the treatment of acromegaly: a study in 64 patients

Cabergoline is a new, long acting, dopamine agonist that is more effective and better tolerated than bromocriptine in patients with hyperprolactinemia. Because dopamine agonists still have a place in the medical management of acromegaly, cabergoline might be a useful treatment. We, therefore, evaluated the effect of long term administration of cabergoline in a large group of unselected acromegalic patients. Sixty-four patients were included in a multicenter, prospective, open labeled study. A subgroup of 16 patients had GH-/PRL-cosecreting pituitary adenomas. Cabergoline was started at a dose of 1.0 mg/week and was gradually increased until normalization of plasma insulin-like growth factor I (IGF-I) levels, occurrence of unacceptable side-effects, or a maximal weekly dose of 3.5 mg (7.0 mg in 1 case) was reached. Treatment with cabergoline suppressed plasma IGF-I below 300 micrograms/L in 39% of cases and between 300-450 micrograms/L in another 28%. With pretreatment plasma IGF-I concentrations less than 750 micrograms/L, a suppression of IGF-I below 300 micrograms/L was obtained in 53% of cases, and a suppression between 300-450 micrograms/L was obtained in another 32%. By contrast, with pretreatment plasma IGF-I concentrations above 750 micrograms/L, only 17% of cases showed a suppression of IGF-I below 300 micrograms/L, and there was IGF-I suppression between 300-450 micrograms/L in another 21%. In GH-/PRL-cosecreting adenomas, 50% of cases suppressed plasma IGF-I levels below 300 micrograms/L, and another 31% did so between 300-450 micrograms/L, in contrast to only 35% and 27%, respectively in GH-secreting adenomas. Similar results were obtained concerning the secretion of GH. Tumor shrinkage was demonstrated in 13 of 21 patients, with a mass reduction by more than half in 5 GH-/PRL-cosecreting adenomas. Except for slight gastrointestinal discomfort and orthostatic hypotension in a few patients at the beginning of therapy, cabergoline treatment was well tolerated. Only 2 patients stopped medication because of nausea. The weekly dose of cabergoline ranged between 1.0-1.75 mg. A further increase in the dose was only effective in 1 GH-/PRL-cosecreting adenoma. The results of this study suggest that cabergoline is an effective, well tolerated therapy that should be considered in the management of acromegaly, especially if the pituitary adenoma cosecretes GH and PRL or if pretreatment plasma IGF-I levels are below 750 micrograms/L.

Cellular abnormalities in pituitary tumors

Pituitary cells appear to be programmed to proliferate in response to cyclic adenosine monophosphate (cAMP), leading to tumorigenesis. Stimulatory neurohormones and inhibitory inputs normally act in opposition to control cAMP levels, but receptor/postreceptor alterations may affect their relative effects. Most growth hormone (GH), corticotropin (ACTH)-, prolactin (PRL)-, and gonadotropin-secreting adenomas and nonfunctioning pituitary adenomas (NFPA) possess specific thyrotropin-releasing hormone (TRH) receptors, normally coupled with cytosolic [Ca2+]i increase and diacyl glycerol production. These cells are also sensitive to other peptides such as vasoactive intestinal peptide (VIP) and pituitary adenylyl cyclase-activating peptide (PACAP), which activate adenylyl cyclase in many hormone-secreting adenomas and in all NFPA. The two main inhibitory agents controlling pituitary function are somatostatin (SS) and dopamine (DA), which have been reported to reduce hormone hypersecretion and tumor growth in a variable percentage of patients. Inhibition of adenylyl cyclase activity and cytosolic [Ca2-]i levels is involved in the transduction of DA signals in normal and tumoral mammotrophs, but in GH-secreting adenomas DA receptors are exclusively and defectively coupled only with [Ca2+]i reduction. The abnormal expression of these receptors can amplify stimulatory signals with both secretory and proliferative potential. The availability of specific G proteins may qualify the cell response to inhibitory agents. For example, in a subset of NFPA, SS alone or DA alone causes an abnormal increase in [Ca2+]i levels due to Ca2+ mobilization from intracellular stores.

Clinical features and differential diagnosis of pituitary tumours with emphasis on acromegaly

Pituitary adenomas are frequently encountered, benign intracranial tumours. Clinically classified according to their capacity to produce and secrete hormones, pituitary tumours are diagnosed from the clinical manifestations and biochemical findings of specific pituitary hormone overproduction or of impaired pituitary function due to pressure on normal pituitary cells, the pituitary stalk or the hypothalamus. Additionally, the tumour may result in neurological manifestations due to its effect as an intracranial space-occupying lesion. Pituitary adenomas may present acutely with pituitary apoplexy after intrapituitary haemorrhage or infarction. The subsequent hypofunction of the pituitary with concomitant neurological sequelae of an expanding intracranial mass are often associated with excruciating headache, diplopia and visual field defects. Gradually developing neurological deficits or secondary endocrine failure over several years may precede the recognition of non-secretory tumours (30-40% of pituitary adenomas) as well as some of the hormone-producing adenomas, especially when they expand beyond the confines of the sella turcica. Asymptomatic masses occur in the pituitary in 5-27% of unselected autopsy series. About 10-20% of pituitaries imaged as part of a brain study contain lesions 'consistent with a pituitary adenoma', with about half being pituitary adenomas ('incidentalomas'). Many advocate screening such cases for a wide spectrum of pituitary function abnormalities. Clinical judgement should be utilized to determine the extent of the work-up and the frequency of follow-up. Acromegaly, a clinical syndrome caused by excess growth hormone secretion, accounts for one-sixth of resected pituitary tumours. This disorder leads to chronic progressive disability and a shortened life span, with approximately 50% of untreated acromegalic patients experiencing premature death. The prevalence of acromegaly has been estimated to range from 50 to 70 per million, with the age of diagnosis usually between the third and fifth decades. Conditions associated with acromegaly include glucose intolerance, diabetes mellitus, lipid abnormalities, cholelithiasis, goitre, and hyperthyroidism, respiratory complications, hypertension, cardiovascular disease, and calcium metabolism abnormalities. An association between acromegaly and cancer, especially of the colon, is now recognized. Epidemiological series have indicated that cancer of the colon, breast and other types of malignancy are a cause of death with increased frequency in acromegalics compared with expected rates. Hypopituitary symptoms secondary to the mass effect of macroadenomas in acromegalic patients are common. Among premenopausal women, menstrual irregularities and galactorrhoea have been reported in 40-70%, while more than half of the men complain of impotence and decreased libido.(ABSTRACT TRUNCATED AT 400 WORDS)

Iodine-123-IBZM-SPECT: studies in 15 patients with pituitary tumors

Single photon emission computerized tomography (SPECT) using the Iodine 123 labeled dopamine D2 receptor antagonist S(-)Iodobenzamide [S (-)IBZM] was performed in 15 patients with pituitary tumors. Among them there were five prolactinoma patients with macroadenoma and two acromegalic patients with macroadenoma. Specific binding in the area of the adenoma was only observed in one subject, a macroprolactinoma patient, who was responsive to dopaminergic treatment. None of the other patients, among them one macroprolactinoma patient responsive to dopaminergic treatment showed specific binding in the area of the tumor. IBZM-binding in the striatum was found to be significantly lower in the group of pituitary tumor patients as compared to controls. The results show that D2 receptors in pituitary adenomas can be visualized using SPECT. However, the sensitivity of IBZM-SPECT appears to be too poor to visualize PRL- and GH- secreting macroadenomas in general.

Body composition in active acromegaly during treatment with octreotide: a double-blind, placebo-controlled cross-over study

OBJECTIVE

In active acromegaly body composition is characteristically altered by an increase in lean body mass and a corresponding reduction in fat mass. These changes are induced by an excessive secretion of GH and insulin-like growth factor I (IGF-I). Growth hormone is an anabolic hormone and leads to stimulation of protein synthesis and an increased lipolysis in adipose tissue. Treatment with the somatostatin analogue, octreotide, has been shown to reduce GH levels causing reduced hormonal effects on target tissues. We have studied changes in body composition during short-term reduction in GH level by octreotide in active acromegaly.

DESIGN

Octreotide was compared to placebo in a double-blind, cross-over trial. Dual-energy X-ray absorptiometry scanning was employed to calculate body composition. Relations between body composition parameters and clinical signs of acromegaly (finger circumference and foot volume) were studied.

PATIENTS

Twelve patients with active acromegaly, confirmed by lack of GH suppression during oral glucose loading, were included. All had pituitary adenomas diagnosed by computed tomography.

MEASUREMENTS

Serum GH and IGF-I. Lean body mass, fat mass and total weight, foot volume and finger circumference.

RESULTS

Four weeks of octreotide treatment caused a 75% decrease in GH levels (n = 10), a reduction in IGF-I from 476 +/- 51.9 (mean +/- SEM) to 233 micrograms/l +/- 46.3 (P < 0.005) and a corresponding decrease in both body weight (2.51 kg +/- 0.41) (P < 0.005) and lean body mass (2.44 kg +/- 0.48) (P < 0.005). No significant changes in fat mass were observed. These findings were paralleled by significant reductions in foot volume (44.50 ml +/- 17) (P < 0.05) and finger circumference (1.3 mm +/- 0.3) (P < 0.05).

CONCLUSIONS

Short-term octreotide therapy reduces growth hormone levels leading to a significant reduction in lean body mass as assessed by dual-energy X-ray absorptiometry. Alterations in lean body mass were positively correlated with reductions in foot volume. Thus, simple clinical tests may be valuable in judging the effects of treatment in active acromegaly.

Treatment with octreotide and bromocriptine in patients with acromegaly: an open pharmacodynamic interaction study

OBJECTIVE

Several studies suggest that the combination of octreotide and bromocriptine is more effective than octreotide alone in reducing GH levels in patients with acromegaly. However, these studies have evaluated either the acute effects of single doses of octreotide and bromocriptine, or the effects of long-term combination therapy, in which octreotide was given only twice a day. The aim of the study was to evaluate the effects of the combination of octreotide and bromocriptine compared to octreotide alone, using a treatment scheme of three daily injections of octreotide during a period long enough to ensure a pharmacokinetic and pharmacodynamic steady state.

PATIENTS

Eleven patients with acromegaly.

DESIGN AND MEASUREMENTS

Different treatment regimes were performed during three periods. During the first period there was no administration of octreotide or bromocriptine, during the second period 100 micrograms octreotide was given subcutaneously three times a day, and during the third period 100 micrograms octreotide was given subcutaneously three times a day in combination with bromocriptine, given orally 5 mg twice daily. When the patients were without any treatment a single oral dose of 5 mg bromocriptine was given at 0730 h. Individual GH levels were assessed as the mean value of 11 observations during the day, at hourly intervals from 0730 to 1530 h, and at 1730 and 1930 h, and the GH levels for the whole group were calculated as the mean of the individual mean values. Serum IGF-I and PRL were measured in fasting samples at 0730 h on the same days as GH, GH, IGF-I, and PRL were evaluated at the end of each treatment regime.

RESULTS

Basal mean GH value for all 11 patients was 54.2 +/- 17.4 mU/l. During octreotide therapy mean GH value was significantly reduced compared to basal mean GH level; 19.86 +/- 6.82 mU/l (P < 0.05). The reduction of mean GH during combination therapy was also significant compared to basal, 18.70 +/- 6.72 mU/l (P < 0.05). Basal mean IGF-I value for all 11 patients was 716 +/- 96 micrograms/l. During octreotide therapy mean IGF-I value was significantly reduced compared to basal mean IGF-I level; 458 +/- 100 micrograms/l (P < 0.05). The reduction of mean IGF-I during combination therapy was also significant compared to basal, 456 +/- 93 micrograms/l (P < 0.05). There was no difference between the levels of mean IGF-I during the two treatment periods. One patient, the only patient with hyperprolactinaemia, showed an additional reduction of GH levels of > 50% during combination therapy. This was also the patient showing the most pronounced reduction of GH levels after the administration of a single dose of bromocriptine.

CONCLUSION

When octreotide is administered three times a day, the additive effect of bromocriptine on GH and IGF-I suppression seems to be negligible in most patients with acromegaly.

Long-term treatment of acromegalic patients with repeatable parenteral depot-bromocriptine

We studied the efficacy and tolerability of a repeatable long-acting parenteral depot-bromocriptine preparation (Parlodel LAR) in 14 acromegalic patients, 10 of whom had received oral bromocriptine therapy previously, 2 of them showing intolerance to oral bromocriptine. Patients received i.m. injections of 50-100 mg depot-bromocriptine at 4-week intervals for 3-24 months (median 6). Growth hormone profiles were assessed by four daily samples at 4-week intervals. Main daily growth hormone levels decreased from 52.1 +/- 12.3 micrograms/l (mean +/- SEM) to 19.4 +/- 4.7 micrograms/l on the day of injection. In 6 patients, growth hormone values were lowered by more than 50%, whereas IGF-I levels decreased only slightly and growth hormone values during the oral glucose tolerance test remained non-suppressible. Tumour sizes were not affected. Two women became pregnant and were delivered of healthy babies. Side-effects typical of bromocriptine occurred frequently on the days of injection and diminished in most patients after 2 months of therapy despite increasing dosage. Compared with previous oral bromocriptine therapy, 9 of 10 patients preferred the depot preparation, whereas the reduction of growth hormone levels was similar during both treatments. In conclusion, depot-bromocriptine should be considered for acromegalic patients intolerant to oral bromocriptine.

Use of octreotide acetate for control of symptoms in patients with islet cell tumors

Gut tumor syndromes are rare, occurring in less than two cases per million population per year: Insulinomas are most common and gastrinomas are less common; all the others are extremely rare. Conventional treatment of the symptoms caused by these tumors has included surgery, hepatic arterial embolization, and chemotherapy; some patients with Zollinger-Ellison syndrome (ZES) have been treated with specific agents such as gastric antisecretory drugs. The development of octreotide, a synthetic, long-acting analogue of the natural peptide somatostatin, has offered an alternative to such therapies. Octreotide has a half life of > 100 minutes and inhibits both physiological- and tumor release of many peptides. It also has direct effects on the gut that modify secretion and motility. Octreotide has been shown to be particularly useful for the symptoms of tumors producing vasoactive intestinal peptide (VIP), and of the carcinoid syndrome. It is also useful in patients with glucagonomas, with growth hormone-releasing hormone producing tumors, and in some patients with Cushing's syndrome and unresectable insulinomas. Octreotide is effective in patients with ZES, but alternative therapies such as omeprazole are more effective, safer, and more convenient for those patients. Side effects of octreotide have not been troublesome in these patients, but the incidence of long term effects is still not entirely clear. Octreotide has proved to be a significant advance in the treatment of patients with islet cell tumors.

The role of Sandostatin in acromegaly

Long-acting somatostatin analogues are extensively used for the treatment of acromegalic patients who have not been cured by surgery or for whom surgery is contraindicated or hazardous. Such an analogue, Sandostatin, has been approved for this indication in various countries and to date an overall review is feasible. From the literature and our experience, clinical response of acromegaly is attained in 60% to 70%, with mainly a reduction in headaches, arthralgias, and acral growth. Hormonal response, evaluated on plasma growth hormone (GH) levels, is observed in more than 80% of the patients. In 36% to 45% of the patients, plasma GH levels are reduced to near-normal values, and in 50% of the patients, the percentage of reduction is greater than 50% of pretreatment values. The major source of concern is the occurrence of gallstones during the treatment; its frequency is evaluated differently. From the largest well-documented series, we retain a percentage of 12.5% of newly occurring cholelithiasis and in most cases they remain asymptomatic. Tumor shrinkage is minor in most cases.

Dopamine, the dopamine D2 receptor and pituitary tumours

Dopamine plays an important role in the hypothalamic-pituitary axis where its major effects are to inhibit pituitary hormone secretion and cell division. Chronic dopamine deficiency has been postulated as a cause of pituitary tumour formation and several lines of evidence exist to suggest that a functional deficiency may develop as a result of defective dopamine receptor action. The available data suggest that a number of sites in the dopamine-D2 receptor-second messenger pathways may be implicated. These abnormalities are reflected in the variety of responses to dopamine and its agonists which have been observed in pituitary tumours both in the clinical situation and in cultured cells in vitro. Whilst it seems likely that the primary defect in pituitary tumour formation lies within the pituitary itself, the role of hypothalamic factors in facilitating tumour growth remains to be explored. Further studies of the dopamine receptor and its function will be of value not only in pathophysiological studies of human pituitary adenomas, but also in the development of new pharmacological agents to treat patients with these tumours.

Long-term treatment with SMS 201-995 in resistant acromegaly: effectiveness of high doses and continuous subcutaneous infusion

Seventeen patients (8 women and 9 men) resistant to all other forms of therapy were treated with the somatostatin analogue SMS 201-995 (octreotide, Sandostatin). The duration of treatment ranged from 1 to 5 years. Mean GH levels of only 4 patients were suppressed under 5 micrograms/L during an 8 h serum profile with the standard dose of 0.1 mg 2 or 3 times daily. This standard dose suppressed mean GH levels in 10 other patients more than 50% of baseline, but for optimal effect higher doses up to 1.5 mg, 4 daily injections or continuous subcutaneous infusion (CSI) were needed. Octreotide had no influence on GH secretion in 3 patients. Suppression of mean GH levels under 5 micrograms/L was achieved in 10 patients. Normalization of insulin-like growth factor I (IGF-I) occurred in only 5 patients. Altogether, therapy with SMS 201-995 reduced GH levels from 23.8 +/- 32.2 micrograms/L (mean +/- SD) to 6.7 +/- 5.0 micrograms/L by 71.8% and IGF-I levels from 7.9 +/- 3.1 U/ml to 3.2 +/- 1.6 U/ml by 59.5%. We conclude that 1) treatment with SMS 201-995 in patients resistant to other forms of therapy may be less successful than previously reported for heterogenous groups of patients; 2) the dose regimen must be adapted to the individual patient for optimal effect and most of our patients needed higher doses than 300 micrograms daily; 3) 4 or maybe more daily injections or CSI seem to be most effective; and 4) in a minority of patients SMS has no influence on GH-secretion.