Clinical and imaging presentations are associated with function in incidental adrenocortical adenomas: a retrospective cohort study.

OBJECTIVE: The aim of this study is to assess whether clinical and imaging characteristics are associated with the hormonal subtype, growth, and adrenalectomy for incidental adrenal cortical adenomas (ACAs). DESIGN: This is a single-center cohort study. METHODS: Consecutive adult patients with incidental ACA were diagnosed between 2000 and 2016. RESULTS: Of the 1516 patients with incidental ACA (median age 59 years, 62% women), 699 (46%) had nonfunctioning adenomas (NFAs), 482 (31%) had mild autonomous cortisol secretion (MACS), 62 (4%) had primary aldosteronism (PA), 39 (3%) had Cushing syndrome, 18 (1%) had PA and MACS, and 226 (15%) had incomplete work-up. Age, sex, tumor size, and tumor laterality, but not unenhanced computed tomography Hounsfield units (HU), were associated with hormonal subtypes. In a multivariable analysis, ≥1 cm growth was associated with younger age (odds ratio [OR] = 0.8 per 5-year increase, P = .0047) and longer imaging follow-up (OR = 1.2 per year, P < .0001). Adrenalectomy was performed in 355 (23%) patients, including 38% of MACS and 15% of NFA. Adrenalectomy for NFA and MACS was more common in younger patients (OR = 0.79 per 5-year increase, P = .002), larger initial tumor size (OR = 2.3 per 1 cm increase, P < .0001), ≥1 cm growth (OR = 15.3, P < .0001), and higher postdexamethasone cortisol (OR = 6.6 for >5 vs <1.8 µg/dL, P = .002). CONCLUSIONS: Age, sex, tumor size, and laterality were associated with ACA hormonal subtype and can guide diagnosis and management. Tumor growth was more common with younger age and longer follow-up. Unenhanced HU did not predict hormonal subtype or growth. Adrenalectomy for MACS and NFA was mainly performed in younger patients with larger tumor size, growth, and elevated postdexamethasone cortisol.

Primary hyperparathyroidism in patients with multiple endocrine neoplasia type 1: Impact of genotype and surgical approach on long-term postoperative outcomes.

BACKGROUND: Protein-truncating germline pathogenic variants in the N- and C-terminal exons (2, 9, and 10) of the MEN1 gene may be associated with aggressive pancreatic neuroendocrine tumors. However, the impact of these variants on parathyroid disease is poorly understood. We sought to investigate the effects of genotype and surgical approach on clinical phenotype and postoperative outcomes in patients with multiple endocrine neoplasia type 1 (MEN1)-related primary hyperparathyroidism. METHODS: We identified patients with MEN1 evaluated at our institution from 1985 to 2020 and stratified them by genotype, (truncating variants in exons 2, 9, or 10, or other variants), and index surgical approach, (less-than-subtotal parathyroidectomy [

Primary Aldosteronism: A Pragmatic Approach to Diagnosis and Management.

Primary aldosteronism is a prevalent but underdiagnosed cause of hypertension, contributing to increased cardiovascular and cerebrovascular events and end-organ damage independent of blood pressure. Prompt diagnosis and treatment with targeted surgical or medical therapy reduce the risk of complications and improve prognosis. This review outlines a practical approach to diagnosis and management of primary aldosteronism for global practitioners.

Glucocorticoid withdrawal syndrome following surgical remission of endogenous hypercortisolism: a longitudinal observational study.

OBJECTIVE: Glucocorticoid withdrawal syndrome (GWS) is a scarcely studied phenomenon that complicates the recovery following surgical remission of hypercortisolism. We aimed to characterize the presence and trajectory of glucocorticoid withdrawal symptoms in the postoperative period and to determine presurgical predictors of GWS severity. DESIGN: Longitudinal observational study. METHODS: Glucocorticoid withdrawal symptoms were prospectively evaluated weekly for the first 12 weeks following surgical remission of hypercortisolism. Quality of life (CushingQoL and Short-Form-36) and muscle function (hand grip strength and sit-to-stand test) were assessed at the baseline and at 12 weeks after surgery. RESULTS: Prevalent symptoms were myalgias and arthralgias (50%), fatigue (45%), weakness (34%), sleep disturbance (29%), and mood changes (19%). Most symptoms persisted, while myalgias, arthralgias, and weakness worsened during weeks 5-12 postoperatively. At 12 weeks after surgery, normative hand grip strength was weaker than at baseline (mean Z-score delta -0.37, P = .009), while normative sit-to-stand test performance improved (mean Z-score delta 0.50, P = .013). Short-Form-36 Physical Component Summary score worsened (mean delta -2.6, P = .015), but CushingQoL score improved (mean delta 7.8, P < .001) at 12 weeks compared to baseline. Cushing syndrome (CS) clinical severity was predictive of postoperative GWS symptomology. CONCLUSION: Glucocorticoid withdrawal symptoms are prevalent and persistent following surgical remission of hypercortisolism with baseline CS clinical severity predictive of postoperative GWS symptom burden. Differential changes observed in muscle function and quality of life in the early postoperative period may reflect the competing influences of GWS and recovery from hypercortisolism.

Determinants of muscle function and health-related quality of life in patients with endogenous hypercortisolism: a cross-sectional study.

OBJECTIVE: Prospective data on determinants of muscle strength impairment and quality of life in patients with various subtypes and severity of endogenous hypercortisolism are lacking. DESIGN: Single-center cross-sectional study, 2019 to 2022. METHODS: Patients with Cushing syndrome (CS) and mild autonomous cortisol secretion (MACS) were assessed with clinical and biochemical severity scores, muscle function (nondominant hand grip strength and sit-to-stand test), and quality of life (Short Form-36 [SF36] and CushingQoL). Referent subjects were recruited from the local population undergoing abdominal imaging for reasons other than suspected adrenal disorder. RESULTS: Of 164 patients, 81 (49%) had MACS, 14 (9%) had adrenal CS, 60 (37%) had pituitary CS, and 9 (5%) had ectopic CS. Median age was 53 years (interquartile range: 42-63 years), and 126 (77%) were women. The SF36 mental component score was similarly low in patients with MACS vs CS, but physical component score was lower in CS when compared to MACS (mean of 34.0 vs 40.5, P = .001). Compared to MACS, patients with CS had lower scores on the standardized CushingQoL (mean of 47.1 vs 34.2, P < .001). Compared to referent subjects, patients with MACS demonstrated reduced muscle strength, similar to patients with CS (mean sit to stand Z-score of -0.47 vs -0.54, P = .822). Clinical severity (r = -0.22, P = .004) but not biochemical severity was associated with sit-to-stand test performance. CONCLUSIONS: Both patients with overt CS and MACS demonstrate reduced muscle strength and low quality of life. The clinical severity score utilized is associated with both physical and psychosocial components of CushingQoL and with the physical component of SF36.

Mediastinal Paraganglioma: A retrospective analysis of 51 cases.

BACKGROUND: Paragangliomas are rarely found in the mediastinum, where they account for a small proportion of mediastinal masses. This study aimed to better characterize the presenting features and relevant aspects in optimizing the diagnosis and treatment of mediastinal paragangliomas. METHODS: A computer-assisted search of electronic health records was performed to identify adult patients (≥18 years) who underwent evaluation for a primary mediastinal paraganglioma at Mayo Clinic between January 2000 and April 2022. Medical charts, laboratory tests and radiology images were reviewed to collect data. RESULTS: The study included 51 patients, each with a single mediastinal paraganglioma. The median age was 47 years (IQR: 39-67), 67% females. Symptoms of catecholamine excess were manifest in 39% of patients, and 14% presented with mass effect, while the remaining 47% had no paraganglioma-related symptoms. Genetic testing was performed in 35 patients; 66% harbored a pathogenic variant in the succinate dehydrogenase enzyme complex. Most paragangliomas (71%) were in the middle mediastinum and showed uptake of intravenous contrast on chest imaging. Biopsies were performed in 30 (59%) patients; 27% were inconclusive and 10% resulted in major complications. Surgical resection occurred in 75%, primarily for relief of symptoms (50%) followed by proximity to critical structures (45%). Perioperative complications were common (66%), but there were no cases of local tumor recurrence during the follow-up period (median 8 years; IQR: 4-13). CONCLUSION: Mediastinal paragangliomas are most located in the middle mediastinum and can often be diagnosed noninvasively using a combination of clinical, biochemical, and radiological features.

Adrenal and juxta-adrenal schwannomas: A single-centre study.

OBJECTIVE: Adrenal schwannomas and juxta-adrenal schwannomas are rare tumours. We aimed to summarise their clinical, biochemical and imaging characteristics. DESIGN: Single-centre retrospective study of eligible patients between 1995 and 2022. PATIENTS AND MEASUREMENTS: Patients with a histopathologic diagnosis of adrenal or juxta-adrenal schwannoma. RESULTS: Twenty-four patients were diagnosed with either primary adrenal schwannoma (8, 33%) or juxta-adrenal schwannoma (16, 67%). Most tumours (21, 88%) were discovered incidentally on imaging. All tumours were unilateral, with 15 (62%) on the left and 9 (38%) on the right. At diagnosis, the median tumour size was 4 cm (range, 2-13 cm). Adrenal schwannomas were smaller when compared to juxta-adrenal schwannomas (median of 3.1 cm [range, 2-9 cm] vs. 4.6 cm [range, 2.3-13.3 cm], p = .037). On imaging, the tumours were round or oval in shape in 16 (70%), lobulated in 7 (30%), solid in 15 (68%), solid-cystic in 7 (32%), heterogeneous in 14 (61%) and homogeneous in 9 (39%). The median unenhanced computed tomography attenuation was 30 Hounsfield units (HU) (range, 12-38 HU). Of the 20 patients who underwent complete hormonal testing, all had nonfunctioning tumours. There was no recurrence or new tumour development in our cohort. CONCLUSIONS: Adrenal and juxta-adrenal schwannomas are nonfunctioning benign tumours that present with indeterminate radiographic features, including large tumour size and increased unenhanced CT attenuation. We did not find an imaging phenotype that was diagnostic of schwannoma. The diagnosis of this rare tumour is based on biopsy or resection.

Clinical, imaging and biochemical presentation of cystic pheochromocytomas.

OBJECTIVE: Cystic adrenal mass is a rare imaging presentation of pheochromocytoma. We aimed to describe the clinical, biochemical and imaging characteristics of patients with cystic pheochromocytoma. DESIGN: Single-centre, retrospective study, 2000-2020. PATIENTS: Consecutive patients with cystic pheochromocytoma were identified from our institutional pathology and adrenal tumour database. RESULTS: Of the 638 patients with pheochromocytomas, 21 (3.2%) had cystic pheochromocytomas (median age: 57 years, 57% women). Most pheochromocytomas were discovered incidentally (57%) or due to symptoms of catecholamine excess (24%). The median tumour size was 6.4 cm. On imaging, cystic pheochromocytomas were round or oval (90%), heterogeneous lesions (86%) with a thick solid rim (median rim thickness 13.9 mm, unenhanced computed tomography (CT) attenuation 40 Hounsfield units (HU), venous-phase CT attenuation 83 HU), and a median cystic component of 40% (unenhanced CT attenuation 17.6 HU, venous-phase CT attenuation 20.4 HU), and rarely with calcifications (15%). All 20 patients with biochemical testing had functioning tumours (adrenergic in 80%, noradrenergic in 20%). Total urinary metanephrine excretion correlated with the volume of the solid component (R2 = .75, p < .0001) but not the cystic component (R2 = .04, p = .4386). All patients underwent adrenalectomy (48% laparoscopic, 52% open), and the median duration of hospital stay was 4 days. CONCLUSIONS: Cystic pheochromocytomas are rare, large tumours with a phenotypic appearance that can masquerade as other adrenal cystic lesions. The degree of biochemical abnormality in cystic pheochromocytomas is associated with the volume of the solid component. All patients with adrenal cysts that have a solid component or an unenhanced attenuation >10 HU should undergo biochemical testing for pheochromocytoma.

Unilateral Adrenalectomy for Primary Aldosteronism Due to Bilateral Adrenal Disease Can Result in Resolution of Hypokalemia and Amelioration of Hypertension.

BACKGROUND: Bilateral idiopathic hyperaldosteronism (IHA) is responsible for 60% of primary aldosteronism (PA) cases. Medical management is standard of care for IHA. Unilateral adrenalectomy (UA) with the intent of debulking total aldosterone production as a palliative measure remains controversial. METHODS: Single-center retrospective review (2010-2020) of patients undergoing UA with a diagnosis of PA due to IHA (lateralization index [LI] on adrenal venous sampling [AVS] < 4). Demographic, pre-operative, intra-operative, and post-operative variables were assessed. Hypertensive regimens were converted to the WHO Defined Daily Dose (DDD). RESULTS: Twenty-four patients were identified, 14, 58% male and mean age 52 ± 10 years. Preoperative hypokalemia was present in 22, 92% of patients. Median number of antihypertensives taken was 3 (interquartile range [IQR], 2-4) and median DDD was 4 (IQR, 3-5.3). Median lateralization index on AVS was 3.52 (range, 1.19-3.88). All operations were performed in minimally invasive fashion. There were no conversions to open procedure, ICU admissions, or post-operative complications. Median follow-up was 10.5 months (range, 1-145 months). Hypokalemia resolved in 17, 76% of patients at last follow-up. Post-operative median number of antihypertensives taken was 1 (IQR, 1-3) and median DDD was 2 (IQR, 0.5-2.75) from 4, P = 0.003. Three (%) patients required continuation of mineralocorticoid receptor antagonists post-operatively. Blood pressure control improved in 65% of patients. CONCLUSION: Unilateral adrenalectomy in the setting of bilateral hyperaldosteronism can improve blood pressure control and stabilize potassium levels in selected patients. Further prospective studies in larger cohorts will be necessary to further define the role of unilateral adrenalectomy in the setting of PA due to bilateral adrenal disease.

Adrenal venous sampling for lateralization of cortisol hypersecretion in patients with bilateral adrenal masses.

OBJECTIVE: The objective of this study was to evaluate the role of adrenal venous sampling (AVS) in guiding the management of patients with corticotropin (ACTH)-independent glucocorticoid secretory autonomy and bilateral adrenal masses. DESIGN AND PATIENTS: A cohort with 25 patients underwent AVS and surgical management. MEASUREMENTS: Cortisol was measured from the adrenal veins (AVs) and inferior vena cava (IVC). AV/IVC cortisol ratio and cortisol lateralization ratio (CLR) (dominant AV cortisol concentration divided by the nondominant AV cortisol concentration) were calculated. Posthoc receiver-operating characteristic curves were generated to determine the specificity of revised AV/IVC cortisol ratio and CLR in differentiating unilateral from bilateral disease. RESULTS: Patients underwent unilateral (n = 21) or bilateral (n = 4) adrenalectomy. The mean AV/IVC cortisol ratio for unilateral adrenalectomy was 12.1 ± 9.6 (dominant) and 4.7 ± 3.8 (contralateral) with a mean CLR of 3.6 ± 3.5. The mean AV/IVC cortisol ratio for bilateral adrenalectomy was 7.5 ± 2.1, with a mean CLR of 1.1 ± 0.6. At a mean follow-up of 22 months, one patient who underwent unilateral adrenalectomy for the predicted bilateral disease developed recurrent mild autonomous cortisol secretion. Posthoc analyses demonstrated a specificity of 95%-100% for unilateral disease with AV/IVC cortisol ratio >9 for one side, <2.0 for the opposite side and a CLR > 2.3. The specificity was 80%-90% for bilateral disease with AV/IVC cortisol ratio >5.1 bilaterally and a CLR < 1.1. CONCLUSIONS: Among patients with bilateral adrenal masses and ACTH-independent autonomous cortisol secretion, AVS can distinguish between unilateral and bilateral disease with high specificity and may guide surgical management.

Role of Multimodality Imaging and Preoperative Management in Intrapericardial Paragangliomas: Experience From a Case Series.

Intrapericardial paragangliomas are rare, highly vascular tumors that frequently adhere to adjacent structures and blood vessels, making surgical resection challenging. In this case series, we discuss the role of multimodality imaging and preoperative embolization in the management of 3 patients presenting with intrapericardial paragangliomas. (Level of Difficulty: Advanced.).

Presentation, Management, and Outcomes of Urinary Bladder Paraganglioma: Results From a Multicenter Study.

CONTEXT: Urinary bladder paraganglioma (UBPGL) is rare. OBJECTIVE: We aimed to characterize the presentation and outcomes of patients diagnosed with UBPGL. METHODS: We conducted a multicenter study of consecutive patients with pathologically confirmed UBPGL evaluated between 1971 and 2021. Outcomes included repeat bladder surgery, metastases, and disease-specific mortality. RESULTS: Patients (n=110 total; n=56 [51%] women) were diagnosed with UBPGL at a median age of 50 years (interquartile range [IQR], 36-61 years). Median tumor size was 2 cm (IQR, 1-4 cm). UBPGL was diagnosed prior to biopsy in only 37 (34%), and only 69 (63%) patients had evaluation for catecholamine excess. In addition to the initial bladder surgery, 26 (25%) required multiple therapies, including repeat surgery in 10 (9%). Synchronous metastases were present in 9 (8%) patients, and 24 (22%) other patients with UBPGL developed metachronous metastases at a median of 4 years (IQR, 2-10 years) after the initial diagnosis. Development of metachronous metastases was associated with younger age (hazard ratio [HR] 0.97; 95% CI, 0.94-0.99), UBPGL size (HR 1.69; 95% CI, 1.31-2.17), and a higher degree of catecholamine excess (HR 5.48; 95% CI, 1.40-21.39). Disease-specific mortality was higher in patients with synchronous metastases (HR 20.80; 95% CI, 1.30-332.91). Choice of initial surgery, genetic association, sex, or presence of muscular involvement on pathology were not associated with development of metastases or mortality. CONCLUSIONS: Only a minority of patients were diagnosed before biopsy/surgery, reflecting need for better diagnostic strategies. All patients with UBPGL should have lifelong monitoring for development of recurrence and metastases.

Histopathology and Genetic Causes of Primary Aldosteronism in Young Adults.

CONTEXT: Due to its rare incidence, molecular features of primary aldosteronism (PA) in young adults are largely unknown. Recently developed targeted mutational analysis identified aldosterone-driver somatic mutations in aldosterone-producing lesions, including aldosterone-producing adenomas (APAs), aldosterone-producing nodules (APNs), and aldosterone-producing micronodules, formerly known as aldosterone-producing cell clusters. OBJECTIVE: To investigate histologic and genetic characteristics of lateralized PA in young adults. METHODS: Formalin-fixed, paraffin-embedded adrenal tissue sections from 74 young patients with lateralized PA (<35 years old) were used for this study. Immunohistochemistry (IHC) for aldosterone synthase (CYP11B2) was performed to define the histopathologic diagnosis. Somatic mutations in aldosterone-producing lesions were further determined by CYP11B2 IHC-guided DNA sequencing. RESULTS: Based on the CYP11B2 IHC results, histopathologic classification was made as follows: 48 APAs, 20 APNs, 2 multiple aldosterone-producing nodules (MAPN), 1 double APN, 1 APA with MAPN, and 2 nonfunctioning adenomas (NFAs). Of 45 APAs with successful sequencing, 43 (96%) had somatic mutations, with KCNJ5 mutations being the most common genetic cause of young-onset APA (35/45, 78%). Of 18 APNs with successful sequencing, all of them harbored somatic mutations, with CACNA1D mutations being the most frequent genetic alteration in young-onset APN (8/18, 44%). Multiple CYP11B2-expressing lesions in patients with MAPN showed several aldosterone-driver mutations. No somatic mutations were identified in NFAs. CONCLUSION: APA is the most common histologic feature of lateralized PA in young adults. Somatic KCNJ5 mutations are common in APAs, whereas CACNA1D mutations are often seen in APNs in this young PA population.

Clinical course and imaging characteristics of benign adrenal cysts: a single-center study of 92 patients.

Objective: Benign adrenal cysts are rare lesions of the adrenal glands. Limited data are available to guide management. We aimed to describe the presentation and outcomes of patients with benign adrenal cysts. Design: Retrospective longitudinal cohort study. Methods: Consecutive patients with histologically or radiologically confirmed adrenal cysts between 1995 and 2021 were identified. Pheochromocytomas and malignancy were excluded. Results: Benign adrenal cysts were diagnosed in 92 patients (53, 57% women) at a median age of 45 years. Mode of discovery was incidental on imaging in 81 (88%), symptoms of mass effect in 9 (9.8%), and others in 2 (2.2%). Majority (89, 97%) of patients had unilateral cysts (45 right, 44 left) with a median size of 48 mm (range 4-200) at diagnosis. On imaging, most cysts were round/oval (85.4%), homogenous (83.2%) lesions with calcifications (64.0%) and no vascular enhancement (97.7%). During a median follow-up of 65 months (range 7-288), adrenal cysts demonstrated minimal enlargement (median size change 6 mm, median growth rate 2 mm/year). On hormonal evaluation, 10% (5/50 tested) had an abnormal overnight dexamethasone suppression test, and 9.5% (4/42 tested) had an abnormal case detection testing for primary aldosteronism. Patients treated with adrenalectomy (46, 50%) were younger (36.9 years vs 50.8 years, P = 0.0009) and had more rapidly enlarging cysts (median growth rate 5.5 mm/year vs 0.4 mm/year, P = 0.0002). Conclusion: Benign adrenal cysts are usually incidentally discovered, non-functional, homogenous lesions without vascular enhancement that demonstrate minimal growth. Adrenalectomy should be reserved for patients with heterogeneous lesions, abnormal hormonal evaluation, or those with mass effect symptoms.

Cardiometabolic Disease Burden and Steroid Excretion in Benign Adrenal Tumors : A Cross-Sectional Multicenter Study.

BACKGROUND: Benign adrenal tumors are commonly discovered on cross-sectional imaging. Mild autonomous cortisol secretion (MACS) is regularly diagnosed, but its effect on cardiometabolic disease in affected persons is ill defined. OBJECTIVE: To determine cardiometabolic disease burden and steroid excretion in persons with benign adrenal tumors with and without MACS. DESIGN: Cross-sectional study. SETTING: 14 endocrine secondary and tertiary care centers (recruitment from 2011 to 2016). PARTICIPANTS: 1305 prospectively recruited persons with benign adrenal tumors. MEASUREMENTS: Cortisol excess was defined by clinical assessment and the 1-mg overnight dexamethasone-suppression test (serum cortisol: <50 nmol/L, nonfunctioning adrenal tumor [NFAT]; 50 to 138 nmol/L, possible MACS [MACS-1]; >138 nmol/L and absence of typical clinical Cushing syndrome [CS] features, definitive MACS [MACS-2]). Net steroid production was assessed by multisteroid profiling of 24-hour urine by tandem mass spectrometry. RESULTS: Of the 1305 participants, 49.7% had NFAT (n = 649; 64.1% women), 34.6% had MACS-1 (n = 451; 67.2% women), 10.7% had MACS-2 (n = 140; 73.6% women), and 5.0% had CS (n = 65; 86.2% women). Prevalence and severity of hypertension were higher in MACS-2 and CS than NFAT (adjusted prevalence ratios [aPRs] for hypertension: MACS-2, 1.15 [95% CI, 1.04 to 1.27], and CS, 1.37 [CI, 1.16 to 1.62]; aPRs for use of ≥3 antihypertensives: MACS-2, 1.31 [CI, 1.02 to 1.68], and CS, 2.22 [CI, 1.62 to 3.05]). Type 2 diabetes was more prevalent in CS than NFAT (aPR, 1.62 [CI, 1.08 to 2.42]) and more likely to require insulin therapy for MACS-2 (aPR, 1.89 [CI, 1.01 to 3.52]) and CS (aPR, 3.06 [CI, 1.60 to 5.85]). Urinary multisteroid profiling revealed an increase in glucocorticoid excretion from NFAT over MACS-1 and MACS-2 to CS, whereas androgen excretion decreased. LIMITATIONS: Cross-sectional design; possible selection bias. CONCLUSION: A cardiometabolic risk condition, MACS predominantly affects women and warrants regular assessment for hypertension and type 2 diabetes. PRIMARY FUNDING SOURCE: Diabetes UK, the European Commission, U.K. Medical Research Council, the U.K. Academy of Medical Sciences, the Wellcome Trust, the U.K. National Institute for Health Research, the U.S. National Institutes of Health, the Claire Khan Trust Fund at University Hospitals Birmingham Charities, and the Mayo Clinic Foundation for Medical Education and Research.

Multiple endocrine neoplasia type 1 in children and adolescents: Clinical features and treatment outcomes.

BACKGROUND: Clinical manifestations and treatment outcomes in children and adolescents with multiple endocrine neoplasia type 1 are not well characterized. METHODS: We conducted a retrospective cohort study of 80 patients with multiple endocrine neoplasia type 1 who commenced tumor surveillance at ≤18 years of age. RESULTS: Fifty-six patients (70%) developed an endocrine tumor by age ≤18 years (median age = 14 years, range = 6-18 years). Primary hyperparathyroidism occurred in >80% of patients, with >70% undergoing parathyroidectomy, in which less-than-subtotal (<3-gland) resection resulted in decreased disease-free outcomes versus subtotal (3-3.5-gland) or total (4-gland) parathyroidectomy (median 27 months versus not reached; P = .005). Pancreaticoduodenal neuroendocrine tumors developed in ∼35% of patients, of whom >70% had nonfunctioning tumors, >35% had insulinomas, and <5% had gastrinomas, with ∼15% having metastases and >55% undergoing surgery. Pituitary tumors developed in >30% of patients, and ∼35% were macroprolactinomas. Tumor occurrence in male patients and female patients was not significantly different. Genetic analyses revealed 38 germline MEN1 mutations, of which 3 were novel. CONCLUSION: Seventy percent of children aged ≤18 years with multiple endocrine neoplasia type 1 develop endocrine tumors, which include parathyroid tumors for which less-than-subtotal parathyroidectomy should be avoided; pancreaticoduodenal neuroendocrine tumors that may metastasize; and pituitary macroprolactinomas.