Prevalence of comorbidities and concomitant medication use in acromegaly: analysis of real-world data from the United States.

PURPOSE: Patients receiving treatment for acromegaly often experience significant associated comorbidities for which they are prescribed additional medications. We aimed to determine the real-world prevalence of comorbidities and concomitant medications in patients with acromegaly, and to investigate the association between frequency of comorbidities and number of concomitantly prescribed medications. METHODS: Administrative claims data were obtained from the IBM® MarketScan® database for a cohort of patients with acromegaly, identified by relevant diagnosis codes and acromegaly treatments, and a matched control cohort of patients without acromegaly from January 2010 through April 2020. Comorbidities were identified based on relevant claims and assessed for both cohorts. RESULTS: Overall, 1175 patients with acromegaly and 5875 matched patients without acromegaly were included. Patients with acromegaly had significantly more comorbidities and were prescribed concomitant medications more so than patients without acromegaly. In the acromegaly and control cohorts, respectively, 67.6% and 48.4% of patients had cardiovascular disorders, the most prevalent comorbidities, and 89.0% and 68.3% were prescribed > 3 concomitant medications (p < 0.0001). Hypopituitarism and hypothalamic disorders, sleep apnea, malignant neoplasms and cancer, and arthritis and musculoskeletal disorders were also highly prevalent in the acromegaly cohort. A moderate, positive correlation (Spearman correlation coefficient 0.60) was found between number of comorbidities and number of concomitant medications in the acromegaly cohort. CONCLUSION: Compared with patients without acromegaly, patients with acromegaly have significantly more comorbidities and are prescribed significantly more concomitant medications. Physicians should consider the number and type of ongoing medications for individual patients before prescribing additional acromegaly treatments.

Growth hormone therapy in adults with growth hormone deficiency: a critical assessment of the literature.

PURPOSE: Growth hormone (GH) therapy has been studied as treatment for clinical manifestations of adult-onset growth hormone deficiency (AO-GHD), including cardiovascular risk, bone health, and quality of life. Patients with AO-GHD typically also have significant history of pituitary pathology and hypopituitarism, which raises the question of what proportion of their clinical presentation can be attributed to GHD alone. Currently, much of the existing data for GH therapy in AO-GHD come from uncontrolled retrospective studies and observational protocols. These considerations require careful reassessment of the role of GH as a therapeutic agent in adult patients with hypopituitarism. METHODS: We contrast results from placebo-controlled trials with those from uncontrolled and retrospective studies for GH replacement in patients with hypopituitarism. We also examine the evidence for the manifestations of AO-GHD being attributed to GHD alone, as well as the data on adults with congenital, life-long untreated isolated GHD. RESULTS: The evidence for increased morbidity and mortality in hypopituitary patients with GHD, and for the benefits of GH therapy, are conflicting. There remains the possibility that the described clinical manifestations of AO-GHD may not be due to GHD alone, but may also be related to underlying pituitary pathology, treatment history and suboptimal hormone replacement. CONCLUSIONS: In the setting of inconsistent data on the benefits of GH therapy, treatment of AO-GHD remains an individualized decision. There is a need for more randomized, placebo-controlled studies to evaluate the long-term outcomes of GH therapy in adults with hypopituitarism.

Biochemical efficacy of long-acting lanreotide depot/Autogel in patients with acromegaly naïve to somatostatin-receptor ligands: analysis of three multicenter clinical trials.

PURPOSE: In clinical research involving acromegalic patients naïve to somatostatin-receptor ligands (SRLs), 19 and 31% of those receiving the SRLs octreotide LAR and pasireotide LAR, respectively, achieved GH < 2.5 ng/mL + normalized IGF-1 concentrations. The proportions achieving control appeared higher in the post-surgery compared with the de-novo setting with pasireotide, but more similar with octreotide. Using pooled data from multicenter clinical trials, we examined the biochemical efficacy of lanreotide depot/Autogel in similar settings. METHODS: Inclusion criteria: Ipsen-sponsored, 48-52-week trials in SRL-naïve acromegalic populations receiving lanreotide depot (60-120 mg); patients were included if de novo (no prior acromegaly treatment) or post-surgery (no medical treatment; radiotherapy allowed unless within previous 3 years). Efficacy endpoints included normalized IGF-1 levels and GH < 2.5 ng/mL + normalized IGF-1 at study end/last value available. ANALYSES: all patients (analysis #1) and subset with baseline GH > 5 ng/mL (analysis #2). RESULTS: Three studies were included. Analysis #1: normalized IGF-1 was achieved by 42% (71/171) of patients overall (post-surgery, 46% [21/46]; de-novo, 40% [50/125]); GH < 2.5 ng/mL + normalized IGF-1 was achieved by 35% (59/171) (39% [18/46] and 33% [41/125], respectively). Analysis #2: normalized IGF-1 levels, 39% (46/118) (post-surgery, 40% [10/25]; de-novo, 39% [36/93]); GH < 2.5 ng/mL + normalized IGF-1, 31% (36/118) (28% [7/25] and 31% [29/93], respectively). CONCLUSION: In these pooled analyses of SRL-naïve patients receiving lanreotide depot, 39-42% achieved IGF-1 control and 31-35% achieved GH and IGF-1 control. Control rates within post-surgery cohorts did not differ markedly from those in corresponding de-novo cohorts.

Decreased quality of life (QoL) in hypopituitary patients: involvement of glucocorticoid replacement and radiation therapy.

PURPOSE: Hypopituitary patients are assumed to have decreased QoL due to GHD. However, in placebo controlled trials, the effects of GH replacement are no different from placebo. Hydrocortisone dose > 20 mg/day and pituitary radiation are independently associated with poorer QoL. We assessed QoL in panhypopituitary GH- deficient patients never treated with GH. METHODS: Study group was divided into: (a) surgery followed by radiation (n = 21) and (b) surgery alone (n = 32). Mean duration of GHD was 71.4 ± 7.8 months and mean daily hydrocortisone dose was 15 ± 0.7 mg. Control group had transnasal surgery for benign sinus conditions (n = 54). RESULTS: AGHDA scores were significantly worse in the entire study group compared to controls (8.1 ± 1.0 vs. 5.1 ± 0.9, p = 0.03). In patients with history of radiation therapy AGHDA scores were significantly worse than in controls (9.1 ± 1.5, p = 0.02) and SNOT-22 (Sino-Nasal Outcome Test) scores were also significantly worse (15.8 ± 2.0 vs. 23.2 ± 3.5, p = 0.04). However, AGHDA scores in patients without history of radiation and on "physiological" dose of hydrocortisone were similar to those in controls (5.1 ± 0.9 vs. 7.3 ± 1.3, p = 0.17). CONCLUSIONS: Replacement with hydrocortisone doses not exceeding 20 mg/day and avoidance of radiation therapy was accompanied by normal QoL in patients not replaced with GH. Thus, we suggest that the decreased QoL in hypopituitary patients may not be due to GH deficiency per se, but rather to high hydrocortisone doses and to aftereffects of cranial radiation.

Correction to: Criteria for the definition of Pituitary Tumor Centers of Excellence (PTCOE): A Pituitary Society Statement.

The original version of this article unfortunately contained an affiliation error in 'Collaborators for The Pituitary Society, Expert Group on Pituitary Tumors' section. Dr. Misa Pfeifer is affiliated with Medical Faculty, University of Ljubljana, Slovenia and the correct email address to contact is misa.pfeifer@gmail.com.

A machine learning approach to predict early outcomes after pituitary adenoma surgery.

OBJECTIVEPituitary adenomas occur in a heterogeneous patient population with diverse perioperative risk factors, endocrinopathies, and other tumor-related comorbidities. This heterogeneity makes predicting postoperative outcomes challenging when using traditional scoring systems. Modern machine learning algorithms can automatically identify the most predictive risk factors and learn complex risk-factor interactions using training data to build a robust predictive model that can generalize to new patient cohorts. The authors sought to build a predictive model using supervised machine learning to accurately predict early outcomes of pituitary adenoma surgery.METHODSA retrospective cohort of 400 consecutive pituitary adenoma patients was used. Patient variables/predictive features were limited to common patient characteristics to improve model implementation. Univariate and multivariate odds ratio analysis was performed to identify individual risk factors for common postoperative complications and to compare risk factors with model predictors. The study population was split into 300 training/validation patients and 100 testing patients to train and evaluate four machine learning models using binary classification accuracy for predicting early outcomes.RESULTSThe study included a total of 400 patients. The mean ± SD patient age was 53.9 ± 16.3 years, 59.8% of patients had nonfunctioning adenomas and 84.7% had macroadenomas, and the mean body mass index (BMI) was 32.6 ± 7.8 (58.0% obesity rate). Multivariate odds ratio analysis demonstrated that age < 40 years was associated with a 2.86 greater odds of postoperative diabetes insipidus and that nonobese patients (BMI < 30) were 2.2 times more likely to develop postoperative hyponatremia. Using broad criteria for a poor early postoperative outcome-major medical and early surgical complications, extended length of stay, emergency department admission, inpatient readmission, and death-31.0% of patients met criteria for a poor early outcome. After model training, a logistic regression model with elastic net (LR-EN) regularization best predicted early postoperative outcomes of pituitary adenoma surgery on the 100-patient testing set-sensitivity 68.0%, specificity 93.3%, overall accuracy 87.0%. The receiver operating characteristic and precision-recall curves for the LR-EN model had areas under the curve of 82.7 and 69.5, respectively. The most important predictive variables were lowest perioperative sodium, age, BMI, highest perioperative sodium, and Cushing's disease.CONCLUSIONSEarly postoperative outcomes of pituitary adenoma surgery can be predicted with 87% accuracy using a machine learning approach. These results provide insight into how predictive modeling using machine learning can be used to improve the perioperative management of pituitary adenoma patients.

Increased Population Risk of AIP-Related Acromegaly and Gigantism in Ireland.

The aryl hydrocarbon receptor interacting protein (AIP) founder mutation R304* (or p.R304* ; NM_003977.3:c.910C>T, p.Arg304Ter) identified in Northern Ireland (NI) predisposes to acromegaly/gigantism; its population health impact remains unexplored. We measured R304* carrier frequency in 936 Mid Ulster, 1,000 Greater Belfast (both in NI) and 2,094 Republic of Ireland (ROI) volunteers and in 116 NI or ROI acromegaly/gigantism patients. Carrier frequencies were 0.0064 in Mid Ulster (95%CI = 0.0027-0.013; P = 0.0005 vs. ROI), 0.001 in Greater Belfast (0.00011-0.0047) and zero in ROI (0-0.0014). R304* prevalence was elevated in acromegaly/gigantism patients in NI (11/87, 12.6%, P < 0.05), but not in ROI (2/29, 6.8%) versus non-Irish patients (0-2.41%). Haploblock conservation supported a common ancestor for all the 18 identified Irish pedigrees (81 carriers, 30 affected). Time to most recent common ancestor (tMRCA) was 2550 (1,275-5,000) years. tMRCA-based simulations predicted 432 (90-5,175) current carriers, including 86 affected (18-1,035) for 20% penetrance. In conclusion, R304* is frequent in Mid Ulster, resulting in numerous acromegaly/gigantism cases. tMRCA is consistent with historical/folklore accounts of Irish giants. Forward simulations predict many undetected carriers; geographically targeted population screening improves asymptomatic carrier identification, complementing clinical testing of patients/relatives. We generated disease awareness locally, necessary for early diagnosis and improved outcomes of AIP-related disease.

Criteria for the definition of Pituitary Tumor Centers of Excellence (PTCOE): A Pituitary Society Statement.

INTRODUCTION: With the goal of generate uniform criteria among centers dealing with pituitary tumors and to enhance patient care, the Pituitary Society decided to generate criteria for developing Pituitary Tumors Centers of Excellence (PTCOE). METHODS: To develop that task, a group of ten experts served as a Task Force and through two years of iterative work an initial draft was elaborated. This draft was discussed, modified and finally approved by the Board of Directors of the Pituitary Society. Such document was presented and debated at a specific session of the Congress of the Pituitary Society, Orlando 2017, and suggestions were incorporated. Finally the document was distributed to a large group of global experts that introduced further modifications with final endorsement. RESULTS: After five years of iterative work a document with the ideal criteria for a PTCOE is presented. CONCLUSIONS: Acknowledging that very few centers in the world, if any, likely fulfill the requirements here presented, the document may be a tool to guide improvements of care delivery to patients with pituitary disorders. All these criteria must be accommodated to the regulations and organization of Health of a given country.

Surgical debulking of pituitary adenomas improves responsiveness to octreotide lar in the treatment of acromegaly.

BACKGROUND: Studies comparing primary medical treatment of acromegaly with surgery are often non-randomized, and not stratified by illness severity. We prospectively compared primary medical therapy with pituitary surgery in patients with acromegaly. All patients had macroadenomas, at least one random human growth hormone (GH) level ≥12.5 ng/mL, elevated IGF-I levels and failure to suppress GH to <1 ng/mL during an oral glucose tolerance test (oGTT). METHODS: Forty-one patients from seven centers were randomized to primary treatment with octreotide LAR, 30 mg every 4 weeks × 3 months (ARM A, N = 15), or pituitary surgery (ARM B, N = 26) using a 1:2 randomization design. Patients cured by surgery (defined as nadir GH during oGTT <1 ng/mL and normal IGF-I) received no subsequent treatment. Those not cured surgically were then treated with octreotide LAR (SubArm B1) for 3 months. RESULTS: Only one of the 15 patients in ARM A (6.7%) had normalization of both GH and IGF-I. In contrast, 13/26 patients had normalization of both GH and IGF-I after surgery alone (50%). Of the remaining 13 patients who did not normalize with surgery alone, treatment with octreotide LAR resulted in a normal nadir GH and normal serum IGF-I in 7 (53.9%). In total, 20/26 in ARM B (76.9%) experienced normalization of defined biochemical acromegaly parameters. CONCLUSIONS: Pituitary surgery alone was more effective than primary medical treatment (p = 0.006), and the combination of surgery followed by medical therapy was even more effective (p < 0.0001). Subjects treated with medical therapy after surgical debulking had a significant improvement in response rate compared to matched subjects treated with primary medical therapy.

The Role of Radiotherapy in Acromegaly.

Radiotherapy has, historically, played a central role in the management of acromegaly, and the last 30 years have seen substantial improvements in the technology used in the delivery of radiation therapy. More recently, the introduction of highly targeted radiotherapy, or 'radiosurgery', has further increased the therapeutic options available in the management of secretory pituitary tumors. Despite these developments, improvements in primary surgical outcomes, an increase in the range and effectiveness of medical therapy options, and long-term safety concerns have combined to dictate that, although still deployed in selected cases, the use of radiotherapy in the management of acromegaly has declined steadily over the past 2 decades. In this article, we review some of the main studies that have documented the efficacy of pituitary radiotherapy on growth hormone hypersecretion and summarize the data around its potential deleterious effects, including hypopituitarism, cranial nerve damage, and the development of radiation-related intracerebral tumors. We also give practical recommendations to guide its future use in patients with acromegaly, generally, as a third-line intervention after neurosurgical intervention in combination with various medical therapy options.

"Micromegaly": an update on the prevalence of acromegaly with apparently normal GH secretion in the modern era.

PURPOSE: Approximately 25 % of cases of clinically active acromegaly cases treated in our academic center between 1996 and 2000, were diagnosed in patients who had elevated plasma IGF-1 levels, but apparently "normal" 24-h mean plasma GH levels. The current study served to update the data for patients with acromegaly referred to our facility, after increasing awareness of this "normal" GH subpopulation throughout the medical community. METHODS: A retrospective chart review was conducted on 157 patients with acromegaly who underwent resection of a confirmed somatotroph pituitary adenoma at the University of Michigan Health System between the dates of 1 Jan 2001 to 23 Sept 2015. RESULTS: Overall prevalence of acromegalic patients with "normal" GH levels, defined as GH <4.7 ng/mL, was 31 %. Over time, the percentage of patients with "normal" GH at diagnosis did not decline: 26 % from 2001 to 2005, 19 % from 2006 to 2010, and 47 % from 2011 to 2015. Mean pituitary tumor size was 1.8 ± 0.1 cm for the group with elevated GH, and 1.2 ± 0.1 cm for the group with "normal" GH (p < 0.001). Percent microadenomas was higher in a group with "normal" GH as compared to those with elevated GH (48 vs. 12 %, p < 0.001), and tumors >2 cm in the maximal diameter were encountered more frequently in the group with elevated GH (43 vs. 14 %, p < 0.001). CONCLUSIONS: Our data show that a substantial percentage of patients with clinical acromegaly have "normal" GH, and therefore strengthens the growing body of evidence which supports the leading role of IGF-1 levels in diagnostic evaluation. At the present time, questions about the natural course of "micromegaly" and treatment benefits compared to the subpopulation with elevated GH levels remain unanswered, but research continues to build on our understanding of the heterogeneous population of individuals.

Tamoxifen as a therapeutic agent in acromegaly.

OBJECTIVE: Administration of high doses of estrogens to patients with acromegaly has been shown to improve symptomatology of acromegaly and glucose tolerance more than 50 years ago. Selective estrogen receptor modulators (SERMs) mimic the effects of estrogen in bone, liver and the cardiovascular system, but function as an anti-estrogen in endometrial and breast tissue. In this study, we evaluated hormonal effects of a SERM, tamoxifen, in active acromegalic patients with particular emphasis on its use in males. DESIGN: We studied 15 men and 2 post-menopausal women with biochemically-active acromegaly despite the fact that other modalities were ineffective in normalizing their insulin-like growth factor-1 (IGF-1) levels. All patients were treated with tamoxifen 20-40 mg daily for 2-11 months (median of 4 months). METHODS: IGF-1 and growth hormone (GH) levels were assessed immediately before the beginning of treatment and at 2-4 monthly intervals thereafter. Baseline and treatment levels of total and bioavailable testosterone were measured in men. RESULTS: Tamoxifen did not affect basal GH secretion, but it decreased circulating IGF-I in 14 patients (82%) by an average of 90 ± 4 mcg/L, (p = 0.005), and normalized plasma IGF-I in 8 patients (47%). Total and bioavailable testosterone levels increased in all evaluable men (n = 8). Tamoxifen was well tolerated. CONCLUSION: Tamoxifen might be useful in the treatment of patients with biochemically-mild active acromegaly, but longer term studies are warranted.

Pituitary carcinoma with endolymphatic sac metastasis.

Pituitary carcinoma is characterized by the presence of a metastatic lesion(s) in a location non-contiguous with the original pituitary tumor. The mechanism(s) of malignant transformation are not known. A 15 year-old male was diagnosed in 1982 with a pituitary macroadenoma and acromegaly (random GH 67 ng/ml and no suppression by oral glucose). His prolactin was normal between 18 and 23 ng/ml. Transcranial resection in July 1983 was followed by radiation therapy. The tumor was immunopositive for GH and prolactin. The proliferation MIB-1 index was 0-1%. With aqueous Octreotide 100 mcg 4× daily both GH and IGF-1 became normal. The patient was lost to follow-up and was treated by his local physician. In 2001, his IGF-1 level was 1271 ng/ml, and his random GH was 1.8-2.4 ng/ml by ILMA despite progressive increase in the dose of Sandostatin LAR to 140 mg/month in divided doses. Prolactin remained normal or minimally increased between 15 and 25 ng/ml. In 2009 he was diagnosed with the tumor in the location of left endolymphatic sac. Histological examination showed low grade pituitary carcinoma strongly immunopositive for prolactin but negative for GH. MIB-1 antibody labeled 0-5% cells. In 2012 endoscopic resection of the pituitary tumor remnant was attempted. Immunohistochemical stains were strongly immunopositive for both prolactin and GH, similar to his original pituitary tumor. The MIB-1 proliferation index was low from 0 to 1%. To our knowledge this is the first case of pituitary carcinoma in the endolymphatic sac region. The dichotomy between the cell population of the pituitary lesion (GH/prolactin producing) and the metastasis (purely prolactin-producing) may suggest that the metastatic pituitary lesion derived from a clone distinct from the original one.

Long-term efficacy and safety of subcutaneous pasireotide in acromegaly: results from an open-ended, multicenter, Phase II extension study.

Pasireotide has a broader somatostatin receptor binding profile than other somatostatin analogues. A 16-week, Phase II trial showed that pasireotide may be an effective treatment for acromegaly. An extension to this trial assessed the long-term efficacy and safety of pasireotide. This study was an open-label, single-arm, open-ended extension study (primary efficacy and safety evaluated at month 6). Patients could enter the extension if they achieved biochemical control (GH ≤ 2.5 µg/L and normal IGF-1) or showed clinically relevant improvements during the core study. Thirty of the 60 patients who received pasireotide (200-900 µg bid) in the core study entered the extension. At extension month 6, of the 26 evaluable patients, six were biochemically controlled, of whom five had achieved control during the core study. Normal IGF-1 was achieved by 13/26 patients and GH ≤ 2.5 µg/L by 12/26 at month 6. Nine patients received pasireotide for ≥24 months in the extension; three who were biochemically controlled at month 24 had achieved control during the core study. Of 29 patients with MRI data, nine had significant (≥20%) tumor volume reduction during the core study; an additional eight had significant reduction during the extension. The most common adverse events were transient gastrointestinal disturbances; hyperglycemia-related events occurred in 14 patients. Twenty patients had fasting plasma glucose shifted to a higher category during the extension. However, last available glucose measurements were normal for 17 patients. Pasireotide has the potential to be an effective, long-term medical treatment for acromegaly, providing sustained biochemical control and significant reductions in tumor volume.

Repeat endoscopic transsphenoidal surgery for acromegaly: remission and complications.

Reported biochemical remission rates following surgical intervention for acromegaly range from 38 to 83%. In patients not achieving surgical remission, few options remain, mostly limited to medical management and radiation therapy. There is debate over whether or not to offer reoperation to patients in whom surgical remission is not achieved with initial resection. Retrospective chart review was undertaken to determine all patients having acromegaly with persistently elevated GH and/or IGF-1 levels after initial pituitary adenoma resection, and who underwent reoperation using endoscopic endonasal approach at a single institution. Biochemical remission was defined as a postoperative GH level <1 ng/mL and a normal postoperative IGF-1 level in the absence of any medical therapy. In total, 14 patients underwent repeat surgical intervention for acromegaly via endoscopic transsphenoidal approach. Of the 14 patients, 8 (57%) achieved biochemical remission following repeat surgical intervention. Lower preoperative GH levels were associated with greater chance of biochemical remission (P = 0.048). New endocrinopathies were seen in 2 patients (14%), and both were transient diabetes insipidus. Meningitis occurred in 2 patients (14%); both were aseptic meningitis with no sequelae. No mortality was encountered. Repeat surgical intervention for acromegaly via endoscopic transsphenoidal approach appears safe and effective. With no mortality and minimal morbidity, repeat surgical intervention via endoscopic transsphenoidal approach appears a reasonable option for these hard-to-treat patients and should be considered for patients in whom surgical remission is not achieved with initial surgery.

Treatment Patterns, Adherence, Persistence, and Health Care Resource Utilization in Acromegaly: A Real-World Analysis.

Context: Treatment of acromegaly is multimodal for many patients, and medical treatments include somatostatin receptor ligands (SRLs), dopamine agonists (DAs), and growth hormone receptor antagonists (GHRAs). However, recent real-world evidence on treatment patterns for patients with acromegaly is limited. Objective: This study evaluated medication usage, treatment changes, adherence, persistence, comorbidities, and health care resource utilization using deidentified data from MarketScan, a US claims database. Methods: Eligible patients (n = 882) were those receiving monotherapy or combination therapy for ≥90 days without treatment gaps. Results: Mean age at diagnosis was 48.6 years; 50.1% of patients were female. Over half (59.4%) had 1 line of treatment (LOT); 23.1% had 2 LOTs; 17.5% had at least 3 LOTs. Most patients (94.6%) initiated treatment with monotherapies. The most common first-line monotherapy treatments were cabergoline (DA, 36.8%), octreotide long-acting release (first-generation SRL, 29.5%), and lanreotide depot (first-generation SRL, 22.5%). Adherence for first-line treatments (proportion of days covered) was higher for first-generation SRLs (lanreotide depot: 0.8) compared with DAs (0.7). Treatment persistence (time between the first treatment record and a change in LOT/censoring) in LOT 1 was higher for GHRAs (24.8 months) and first-generation SRLs (20.0 months) compared with DAs (14.4 months). Female patients and those diagnosed at a younger age were more likely to have shorter treatment persistence. The most prevalent comorbidities were hyperlipidemia, essential hypertension, and sleep apnea. Conclusion: Patients with more comorbidities had more health care visits during the first year after diagnosis, suggesting increased disease burden. Real-world evidence on treatment patterns provides insights into recommendations for individualized therapy.

Suppression in growth hormone during overeating ameliorates the increase in insulin resistance and cardiovascular disease risk.

Previously, we reported that overeating for only a few days markedly suppressed the secretion of growth hormone (GH). The purpose of the present study was to determine the role of this reduction in GH concentration on key metabolic adaptations that occur during 2 wk of overeating. Nine nonobese, healthy adults were admitted to the hospital for 2 wk, during which time they ate ∼4,000 kcal/day (70 kcal·kg fat-free mass(-1)·day(-1); 50% carbohydrate, 35% fat, and 15% protein), and their plasma GH concentration was allowed to decline naturally (control). An additional eight subjects underwent the same overeating intervention and received exogenous GH treatment (GHT) administered in four daily injections to mimic physiological GH secretion throughout the 2-wk overeating period. We measured plasma insulin and glucose concentrations in the fasting and postprandial state as well as fasting lipolytic rate, proteolytic rate, and fractional synthetic rate (FSR) using stable-isotope tracer methods. GHT prevented the fall in plasma GH concentration, maintaining plasma GH concentration at baseline levels (1.2 ± 0.2 ng/ml), which increased fasting and postprandial assessments of insulin resistance (P < 0.05) and increased fasting lipidemia (all P < 0.05 vs. control). In addition, preventing the suppression in GH with overeating also blunted the increase in systemic proteolysis (P < 0.05 GHT vs. control). However, GHT did not alter lipolysis or FSR in response to overeating. In conclusion, our main findings suggest that the suppression in GH secretion that naturally occurs during the early stages of overeating may help attenuate the insulin resistance and hyperlipidemia that typically accompany overeating.