Citations

Abstract Disclosure: J. Saini: None. S. Singh: None. A.L. Ebbehøj: None. C.D. Zhang: None. R. Nathani: None. V. Fell: None. E. Atkinson: None. S. Achenbach: None. A. Rivard: None. R.J. Singh: None. S.K. Grebe: None. I. Bancos: None. Abstract Context: Mild autonomous cortisol secretion (MACS) is diagnosed based on post-dexamethasone cortisol>1.8 mcg/dL. Scarce evidence exists on steroid circadian secretion and steroid metabolome in MACS. Objective: To characterize 24-hour urine steroid metabolome in patients with MACS and determine circadian differences in urine steroid profiling and cortisol concentrations in patients with MACS versus referent subjects. Design: Cross-sectional study, 2018-2023. Setting: Referral center Participants: 72 patients with MACS and 72 age-, sex-, BMI-, and menopausal status-matched referent subjects. Measurements: Urine was collected over a 24-hour (h) period in separate day- and night-time collections. High-resolution mass spectrometry assay was used to measure 25 steroids. A subgroup of patients and referent subjects were admitted for every 2-hour serum measurement of free and total cortisol. Outcomes: Steroids, sums, and ratios Results: Patients with MACS had lower mcg/24h median androgens (2084 vs 3283, P<0.001), higher glucocorticoids (15754 vs 12936, P<0.001), and higher glucocorticoid/androgen ratio (8.7 vs 3.9, P<0.001). Steroid day/night ratios were lower in patients when compared to referent subjects, reflecting a higher relative nocturnal steroid production in MACS. In a subgroup of 12 patients with MACS and 10 referent subjects, the 24-hour area under the curves for total and free cortisol were similar. However, nocturnal mean total (5.3 vs 4.0 mcg/dL, P=0.056) and free (0.2 vs 0.1 mcg/dL, P=0.035) cortisol were higher in patients vs referent subjects. Conclusion: Patients with MACS demonstrate an abnormal urine steroid metabolome, with a high glucocorticoid to androgen ratio, and a higher nocturnal steroid production. Presentation: 6/3/2024

Abstract Disclosure: H.M. Heshmati: None. H.S. Abu-Lebdeh: None. Background: Fibroblast growth factor 21 (FGF21), a member of the human FGF superfamily, is a 181 amino acid peptide hormone primarily produced by the liver. The gene of FGF21, located on chromosome 19, was cloned in 2000. FGF21 is involved in the maintenance of metabolic homeostasis. This review presents an update on the relevance of FGF21 in the diagnosis and treatment of metabolic disorders including obesity, nonalcoholic fatty liver disease (NAFLD), dyslipidemia, and type 2 diabetes. Methods: A systematic search of literature was conducted using the search terms fibroblast growth factor 21, obesity, nonalcoholic fatty liver disease, dyslipidemia, and type 2 diabetes. Results: FGF21 is a stress hormone with effects on energy expenditure and metabolism of lipids and glucose. FGF21 exerts its endocrine action in the central nervous system and adipose tissue. The serum FGF21 levels in normal subjects increase with aging. Stressful conditions (e.g., fasting status, protein restriction, exercise, metabolic disorders, kidney diseases, cardiovascular diseases, and sepsis) increase FGF21 secretion. Serum FGF21 levels are increased in obesity, NAFLD, dyslipidemia, and type 2 diabetes. Some of these patients may have a state of FGF21 resistance. The resistance to FGF21 is related, at least in part, to the presence of high circulating levels of fibroblast activation protein, a protease that inactivates FGF21. It has been suggested that the exercise-induced weight loss can be due to increased FGF21 secretion and decreased FGF21 resistance in adipose tissue. Serum FGF21 level has the potential to be used as a biomarker for early diagnosis of metabolic disorders (e.g., NAFLD and type 2 diabetes). Based on different metabolic properties of FGF21, FGF21-based therapy has been considered as an attractive approach for the treatment of metabolic disorders. Since native FGF21 has poor pharmacodynamic properties (e.g., short half-life and proteolytic cleavage by proteases), long-acting FGF21 analogs (e.g., LY2405319, PF-05231023, pegozafermin, AKR-001, and LLF580) have been synthesized and tested in clinical trials for the treatment of obesity, NAFLD, dyslipidemia, and type 2 diabetes. The available results show that FGF21 analogs can reduce body weight, liver fat, blood lipids, and fasting insulin/insulin resistance. Overall, the treatment with these analogs is safe and well tolerated. Conclusion: FGF21 is a predominantly liver-derived peptide hormone regulating energy expenditure and metabolism of lipids and glucose. Serum FGF21 levels are increased in several metabolic disorders including obesity, NAFLD, dyslipidemia, and type 2 diabetes. FGF21 is an attractive target for the treatment of these metabolic disorders. Despite some promising results observed with the use of FGF21 analogs, more clinical studies are needed before recommending FGF21-based therapies in metabolic disorders. Presentation: 6/2/2024

Abstract Disclosure: J. Saini: None. B. Salama: None. S.R. Chacko: None. K. Yu: None. I. Bancos: None. Objective: Measurement of baseline dehydroepiandrosterone sulfate (DHEAS) is suggested by the guidelines in support of diagnosing mild autonomous cortisol secretion (MACS). However, evidence on the diagnostic accuracy of DHEAS in MACS is difficult to interpret due to differences in the diagnostic cutoffs, small sample size, and heterogeneous reference standards. We aimed to conduct a systematic review and meta-analysis of published literature to assess the performance of DHEAS in diagnosing MACS, as defined in the 2023 guidelines. Methods: A comprehensive search was conducted using several databases from each database’s inception to January 8th, 2024. Databases include Ovid MEDLINE (R) and Epub Ahead of Print, In-Process & Other Non-Indexed Citations, and Daily, Ovid EMBASE, Ovid Cochrane Central Register of Controlled Trials, Ovid Cochrane Databases of Systematic Reviews, and Scopus. Only original studies of at least 20 participants were included. MACS was defined as post-dexamethasone cortisol >1.8 mcg/dL. QUADAS-2 was used to assess the risk of bias. Bivariate and random effects meta-analysis was used to generate pooled diagnostic accuracy estimates. Results: The initial search yielded 285 articles, and only 7 studies met the inclusion criteria. In 7 studies (1 from North America, 3 from Asia, and 3 from Europe), a total of 574 patients with MACS and 830 referent subjects (patients with adrenal tumors without MACS) were included. The mean age was specified only in 5 studies and was similar in patients with MACS (55.5 years) and referent group (53.3 years). Patients with MACS had a higher number of women (323/472, 68.4%) as compared to the referent group (352/658, 53.4%). DHEAS cutoffs studied included: lower cutoff of age-and sex-specific ranges (3 studies), 40 mcg/dL (3 studies), 60 mcg/dL (1 study), and 67.5 mcg/dL (1 study). With increasing DHEAS cutoff, sensitivity for MACS diagnosis increased, and specificity decreased. Most studies (4 studies) used the chemiluminescent immunoassay to measure DHEAS. A meta-analysis of studies using DHEAS cut-off between 40-70 mcg/dL was performed, with a pooled sensitivity of 68% (95% CI: 51-81) and a pooled specificity of 85% (78-89). The positive likelihood ratio was 4 (95% CI: 3-6; I2=36.94, P=0.175) and the negative likelihood ratio was 0.4 (0.3-0.6; I2=49.97, P=0.092). Most studies were at a high risk of bias for selection of patients, index, or reference standard. Conclusion: Based on limited heterogeneous evidence, measurement of DHEAS provides additional value in diagnosing MACS. Further larger diagnostic accuracy studies should explore various DHEAS cutoffs and consider assay variability. Presentation: 6/3/2024

Abstract Disclosure: A. Verma: None. F. Elli: None. S. Rao: None. M. Smith: None. A. Shapiro: None. C. Moshe: None. R. Chadha: None. Introduction: Pheochromocytomas are rare, neuroendocrine tumors derived from chromaffin cells of the neural crest, typically within the adrenal medulla. The pathophysiologic effect of primary concern is the uncontrolled release of catecholamines into the bloodstream, which carry risk for episodic hypertension, palpitations, and life-threatening crises. Preoperative preparation with drugs that block adrenergic receptors is utilized to improve hemodynamic oscillation force and surgical outcomes. Widely used premedication include alpha-blockers, beta-blockers, and calcium channel blockers. Despite adequate pretreatment, hemodynamic instability continues to evoke massive risk. The objective of this study was to assess the incidence of intraoperative hypertensive episodes in patients undergoing robotic assisted laparoscopic adrenalectomy. Methods: This study is an observational retrospective analysis of patients who underwent elective laparoscopic robotic-assisted adrenalectomies from February 2019 to April 2023. 17 patients total patients were included. Preoperative information included age, BMI, ASA physical classification, preoperative blockade regiment, and urine metanephrines. Intraoperative information included operation duration, tumor size, intraoperative anti-hypertensives, and hypertensive spikes defined as a SBP greater than 175 mmHg for 5 consecutive minutes. Data analysis was performed to obtain frequency counts (%), means (standard deviations), and median (range) as appropriate. Results: The mean age at the time of surgery was 57.12 ± 17.2 years. The majority of patients (76%) were ASA status class III. 7 of the 17 patients did not have active pheochromocytoma based on symptomatology, the incidental diagnoses being made by imaging and workup. The average tumor diameter was 3.90 ± 1.8, with a range of 2.0 - 8.0. Mean operative time was 153.76 ± 53.9 minutes. Preoperative urinary metanephrines were observed to have a mean of 1,248.44 ± 2,866.9 pg/mL. In terms of preoperative preparation, 65% of patients received Doxazosin, and 29% of patients received an alternative anti-hypertensive. Yet, 64.7% of patients were found to have at least 1 intraoperative hypertensive spike Conclusion: Despite premedication with anti-hypertensives, a significant percentage of patients experienced intraoperative hemodynamic instability. This emphasizes the importance of anesthesiologist preparation for intraoperative hypertension management to aggressively prevent hypertensive crises. In addition, it questions the routine use of alpha blockade for all cases preoperatively as has been suggested in certain studies, and whether or not it should be driven by other patient characteristics. Presentation: 6/1/2024

Abstract Disclosure: K.N. Grennan: None. S. Thota-Kammili: None. A.L. McKenna: None. C.G. Coyle: None. S.L. Samson: None. Introduction: Supplement misuse in the bodybuilding community is prevalent. With the availability of internet ordering and purchasing, patients have access to hormonal supplements without prescription or regulation. Here we present the case of a patient on self-administered hormonal supplements who presented in acute heart failure leading to cardiogenic shock in the setting of concurrent thyroid, adrenal, and gonadal axis dysfunction. Case Description: A 28-year-old male with no significant medical history was transferred to our hospital after presenting to an outside emergency room with dyspnea, cough, nausea, and a subjective fever. He developed acute hypoxic respiratory failure requiring intubation. Echocardiogram performed showed an ejection fraction (EF) of 10%. He was started on two vasopressors and methylprednisolone 1 g daily for two days, due to concern for myocarditis versus giant cell arteritis. Hormonal work-up showed TSH 0.02 mIU/L (normal range 0.3-4.2), free T4 0.4 ng/dL (0.9-1.7), total T3 48 ng/dL (80-200), FSH <0.3 IU/L (1.2-15.8), LH <0.2 IU/L (1.3-9.6), ACTH <5.0 pg/mL (7.2-63), cortisol 1.7 mcg/dL (2.5-12), estradiol 171 pg/mL (8.0-35), total testosterone 1730 ng/dL (240-950), and prolactin 47 ng/mL (4.0-15.2). He received 10 mg dexamethasone at the outside facility. A medication bag found by his family included online purchases of non-prescribed testosterone cypionate and enanthate, liothyronine, anastrozole, and clomiphene. None were medical grade. He was also taking the anabolic steroid clenbuterol for 3 days prior. Echocardiogram on day 3 of admission showed an improved EF of 36%. Cardiac magnetic resonance imaging (MRI) showed a papillary fibroelastoma and myocarditis. Patient was weaned off vasopressors and the ventilator. He was discharged on levothyroxine 50 mcg daily and hydrocortisone 10 mg twice daily for outpatient reassessment. Transesophageal echocardiogram confirmed diagnosis of papillary fibroelastoma. One month Endocrinology clinic follow-up showed no evidence of posterior pituitary, thyroid, or adrenal axis dysfunction or growth hormone excess, but he continued to have gonadal axis suppression with elevated prolactin and estradiol, the latter thought to be secondary to conversion from testosterone. Pituitary MRI showed no micro or macroadenoma. His EF recovered to 50%. He is pending surgical removal of the aortic valve fibroelastoma. Discussion: With hormonal supplements easily accessible online, it is important for physicians to counsel patients about the dangers of misuse. This case highlights a previously healthy 28-year-old man who presented in critical condition with cardiogenic shock and hypothalamic-pituitary axis dysfunction from supplements he purchased online. There should be targeted educational interventions regarding the harm of supplements aimed at the bodybuilding community to prevent similar cases. Presentation: 6/2/2024

Abstract Disclosure: P.L. castellanos: None. A.M. Chindris: None. S. Rao: None. J. Janus: None. R. Paz-Fumagalli: None. V.J. Bernet: None. Introduction: Limited information exists regarding the relationship between outcomes and decision-making based on results from Ultrasound-guided fine needle aspiration (USG-FNA) of cervical nodes/nodules suspicious for thyroid cancer metastases. Management options for positive findings include surgery, percutaneous ethanol ablation, radioactive iodine therapy, external beam radiation systemic therapy, or observation. This retrospective review is aimed at describing the management and associated outcomes of a cohort of thyroid cancer patients who underwent USG FNA for cervically metastases. Methods: Following our Clinic IRB review and approval, we performed a chart review and identified 163 patients with thyroid cancer patients who had undergone USG FNA of apparent cervical metastases at the Florida campus between 2012 and 2018. Cytology results and corresponding tumor marker washout from each sampled focus were recorded. The records review included recording anatomical and biochemical outcomes related to management decisions based on USG FNA results. Appropriate statistical plots were used to help visualize the data pattern. ResultsThe median age was 59 years 69.9% were female and 91.3% were Caucasian. Initial presentation typically consisted of the appearance of a neck nodule and thyroidectomy was the first line of therapy in 155 of 163 cases. Imaging post-thyroidectomy demonstrated evidence of cervical lymphadenopathy in 75.5% of cases with localization in the lateral neck in 65.2% and central in 19.2% respectively. Regarding USG-FNA outcomes, 46.2% yielded malignancy while 26% were benign. The most prevalent cytology was papillary thyroid cancer detected in 87.1%.Thyroglobulin washout was performed on all patients with a history of papillary variant thyroid carcinoma, with positive results reported in 8.3%. Ethanol ablation was the most used treatment for lymph node recurrence followed by neck surgery in 56.2%. During the follow-up, 14% of the patients who were TGAB+ remained so.Outcome trends were as follows: The combined anatomical and biochemical negative was 82.3%, while the combined anatomical and biochemical positive was 2.5%. The combined anatomical negative and biochemical positive was 7.6%, alongside the combined anatomical positive and biochemical negative was 7.6%. Conclusion: Of 163 thyroid cancer cases with cervical lymphadenopathy, 46% had cytology-proven presence of malignancy. These patients underwent either observation, PEA, or surgery.At follow up the majority of the patients were without anatomical and biochemical evidence of disease while about 7-8% were positive by one of the parameters and much fewer were positive for disease by both parameters. Presentation: 6/3/2024

Abstract Disclosure: J. Saini: None. V. Fell: None. B. Atkinson: None. S. Achenbach: None. I. Bancos: None. Background: Patients with mild autonomous cortisol secretion (MACS) have a higher prevalence of frailty and reduced muscle strength as compared to patients with nonfunctioning adrenal adenomas or subjects without adrenal disorders. Objective: To determine the impact of adrenalectomy on frailty and parameters of functional strength in patients with MACS. Methods: We conducted a single-center prospective longitudinal study of adults with MACS scheduled for adrenalectomy and referent subjects evaluated between 2018 and 2023. MACS was defined as serum cortisol>1.8 mcg/dL after 1 mg dexamethasone suppression test in patients with adrenal adenomas and no features of overt hypercortisolism. Referent subjects were included if they had abdominal imaging and had no adrenal disorders. Patients and referent subjects had a baseline and a follow-up evaluation at least 10 months later. Differences were assessed using paired t-tests for (1) Frailty Index (FI)--calculated using a questionnaire containing 47 variables on comorbidities, symptoms, and daily living activities (frailty defined as FI>0.25) (2) physical function assessed using handgrip strength (Jamar Plus digital hand dynamometer), timed up-and-go test (time taken to rise from a chair, walk to and from 3 m, and sit down), gait speed, 6-minute walk test, and (3) Advanced Glycation End (AGE) Product (using AGE reader). Results: We evaluated 41 patients before and after adrenalectomy, and 31 referent subjects at baseline and follow-up visit, at a similar interval (median 1.6, IQR 1.2-2.0 vs 1.5 years, IQR 1.0-2.2, P=0.759). While sex distributions were no different between the 2 groups (women, 66% vs 84%, P=0.086), patients with MACS were older than the referent group (median age 57.3, IQR 48.8-66.9 vs 49.0, IQR 41.7-57.9 years, P=0.005). Post-adrenalectomy, FI decreased by a mean of 0.057 (SD 0.08), P<0.001 in patients, and remained unchanged in the referent group. AGE decreased in patients by 0.148 (SD 0.45), P=0.04 but not in referent subjects (-0.047, SD 0.242, P=0.5). Patients demonstrated no improvement in parameters of muscle strength: gait speed (mean change 0.305 m/s, P=0.453), 6-minute walk test (mean change 16.4 meters, P=0.201), dominant (mean Z score change -0.055, P=0.72) and nondominant (mean Z score change -0.199, P=0.192) hand grip muscle strength. At follow-up, both patients (mean change 1.897 seconds, P<0.001) and referent subjects (mean change=1.475 seconds, P<0.001) demonstrated a deterioration on the timed up-and-go test. Conclusions: While no improvement was seen in the parameters of muscle strength, adrenalectomy improved the frailty index in patients with MACS. In addition, AGE, a biomarker associated with cardiovascular morbidity, decreased after adrenalectomy, suggesting a beneficial cardiovascular impact of MACS reversal. Presentation: 6/1/2024

Abstract Disclosure: M. Vahidi Rad: None. S. Ahmed: None. A. Kumar: None. Introduction: Granulomatous disease can cause hypercalcemia due to increased production of 1,25 dihydroxyvitamin-D. Mycobacterium avium complex (MAC) infection is an AIDS (acquired immunodeficiency syndrome)-defining illness and a granulomatous disease that can lead to hypercalcemia. We report a case of severe hypercalcemia from Immune Reconstitution Inflammatory Syndrome (IRIS) in a patient with AIDS and disseminated MAC which developed several months after initiation of appropriate antibiotic and antiviral therapy. Clinical Case: A 30-year-old female with HIV on anti-retroviral therapy and disseminated MAC infection on antibiotics developed PTH independent mild hypercalcemia in the 10.9-11.5 mg/dL range about 4 months after initiation of antiviral and antibiotic therapy. 1,25 dihydroxyvitamin D level was normal at 50 pg/mL (reference range 18-78 pg/mL). The hypercalcemia worsened and about 8 months after initiation of antimicrobial therapy, she had a hospitalization for severe hypercalcemia with corrected calcium of 15.2 mg/dL and acute kidney injury. PTH was suppressed at 6.9 pg/mL and repeat 1,25 dihydroxyvitamin D level was elevated at 129 pg/mL (reference range 18-78 pg/mL). Other testing for PTH independent hypercalcemia including PTH- Related Peptide, serum protein electrophoresis (SPEP) and TSH were normal. She was diagnosed with hypercalcemia from increased calcitriol production in the setting of IRIS secondary to disseminated MAC. Hypercalcemia secondary to increased production of calcitriol in patients with MAC and HIV infection might happen or worsen months after starting the antimicrobial treatments and has been reported as a potential manifestation of immune reconstitution. MAC-associated IRIS has been reported to be associated with a T-helper cell response with increased number of interferon-gamma-producing T-cells and Th1-cytokines that can potentially cause a granulomatous reaction. These granulomas will have increased macrophage 1-alpha-hydroxylase activity that can further result in more production of 1,25 dihydroxyvitamin D3 and cause more hypercalcemia. Prednisone was started with resultant improvement in hypercalcemia. Conclusion: Severe hypercalcemia due to worsening of subclinical granulomatous infections such as MAC can be a manifestation of IRIS in patients with HIV infection or AIDS who are on antiretroviral treatments. This responds to glucocorticoids. Presentation: 6/2/2024

Abstract Disclosure: M. Salama: None. R. Basmaci: None. T. Rajjo: None. O. Chuzhyk: None. A.N. Lteif: None. A. Al Nofal: None. Objective: Heightened societal acceptance of transgender youth and increased awareness of their unmet medical needs have led to a rise in referrals for hormonal therapy. There is limited literature available on the metabolic outcomes of hormone therapy on transgender youth. We investigated how the different metabolic markers of cardiovascular disease change after the initiation of gender-affirming hormonal therapy in transgender adolescents. Methods: A Retrospective, observational cohort study based on chart review of all children with gender dysphoria (under 18 years of age) who were evaluated in the Pediatric Endocrinology Clinic in a tertiary care center between January 2015 and December 2022. Children's demographic information, baseline weight, height, BMI, hematocrit, lipid profile, ALT, prolactin, and HbA1C levels were obtained before and after the initiation of gender-affirming hormonal therapy. The Wilcoxon signed-rank test was employed for paired analysis, while the chi-square test was used as appropriate. Results: We identified 106 transgender youth who were included in the analysis, with a median age at the start of hormonal therapy of 16 years (IQR: 15-17); comprising 68 trans-males (64%) and 38 trans-females (36%). The median treatment duration was 34 months (IQR: 18-54). Among trans-males, ALT levels increased post-treatment (mean difference 6.851 U/L, p < 0.001), as did BMI Z scores (mean difference 0.257, p < 0.001) and LDL-C (mean difference 12.734 mg/dl, p = 0.002), triglycerides (mean difference 10.18 mg/dl, p = 0.009), non-HDL-C (mean difference 12.8 mg/dl, p = 0.002), and total cholesterol (mean difference 10.18 mg/dl, p = 0.02). No significant differences were observed in HbA1C and HDL-C post-treatment. Among transfemales, BMI Z-scores were higher post-treatment (mean difference 0.27, p = 0.007), with increased total cholesterol (mean difference 19.88 mg/dl, p = 0.008), LDL-C (mean difference 12.6 mg/dl, p = 0.02), and HDL-C (mean difference 11.38 mg/dl, p < 0.001). Other variables did not significantly differ pre-and post-treatment. Ten transfemales with measured prolactin levels pre- and post-treatment showed no statistically significant differences. Conclusion: This pilot study revealed increased BMI Z scores following the commencement of hormone therapy in both trans-male and trans-female youths. Moreover, masculinizing treatment led to increased ALT levels. Furthermore, the cardiometabolic profile exhibited diverse alterations, particularly higher LDL-C levels in both cohorts. These findings underscore the necessity for close monitoring of these parameters during the treatment of transgender youth. Larger prospective randomized controlled trials are essential to comprehensively assess the impact of gender-affirming therapy on transgender youth. Presentation: 6/2/2024

Abstract Disclosure: J. Herndon: None. W.G. Breen: None. N. Laack: None. W.S. Harmsen: None. D.Z. Erickson: None. Background: Treatment of chordomas and parasellar meningiomas includes surgical resection and/or various forms of radiotherapy. Proton beam therapy (PBT) is able to provide higher doses of radiation to the targeted tissues while better sparing surrounding structures, potentially facilitating decreased toxicity. While proton utilization has increased, there is a paucity of data regarding short- and long-term endocrinologic outcomes in these patients. Objective: Determine rate of hypopituitarism in patients with chordomas and parasellar meningiomas undergoing PBT. Methods: A prospectively maintained radiation database including adult patients treated with PBT since 2015 at a tertiary referral center for chordomas and parasellar meningiomas was reviewed. Data collected at baseline included demographic data, tumor diagnosis and pathology, prior history of surgery/radiation, radiation treatment, biochemical hormonal data, and incidence of pituitary insufficiencies (PI). Biochemical pituitary hormonal data and incidence of new PI was recorded at 6 months, 1 year, 2 years, 3 years, 4 years, 5 years, and up to two additional time points up to 10 years post-PBT. Statistical analysis includes descriptive statistics presented as number (%) and median [IQR]. Results: Of 177 patients with sellar/parasellar masses with sufficient endocrine data who underwent PBT, a total of 64 patients (36.2%) were included; 40 (62.5%) with parasellar meningioma and 24 (37.5%) with chordoma. Median age of patients was 49.5 years old [37.7, 63.2], and 44 (68.8%) were female. Median follow-up was 24 months [12, 36]. Prior to PBT, 52 patients (81.3%) were treated surgically, 5 (7.8%) had prior fractionated photon or gamma-knife radiation therapy. At baseline 10 patients (15.6%) exhibited PI in at least one pituitary axis, most commonly secondary hypogonadism (7, 70%). Median PBT total prescribed dose was 54 Gy [50.4, 70.0] in a median of 30 [28, 35] fractions. Cumulative incidence of newly diagnosed PI at follow-up was 4.7% at 6 months, 9.4% at 1 year, 14.1% at 2 years, and 17.2% at 3+ years. No patients with PI at baseline developed new deficiencies. Among the 11 patients (17.2%) who developed new PI, 17 various deficiencies were recorded (range 1-3 per patient), including hypogonadism (8, 47.1%), hypothyroidism (6, 35.3%), and adrenal insufficiency (4, 23.5%). No growth hormone deficiency was clinically diagnosed, however IGF-1 levels decreased from baseline at the follow-up (when available) by a median of -11.8 ng/mL at 6 months (n = 12), -3.0 at 1 year (n = 12), -17.0 at 2 years (n = 7), -30.5 at 3 years (n = 4), -55.0 at 4 years (n = 3), and -37.5 at 5 years (n = 2). Conclusion: Incidence of newly developed PI in chordomas and parasellar meningiomas following PBT for adult patients after median initial follow up of 2 years was low, however extended follow up data are necessary. Presentation: 6/1/2024