Endocrine Abstracts

JOINT1876

Introduction: A spectrum of metabolic alterations in acromegaly predisposes patients to diabetes mellitus, with chronic overproduction of growth hormone (GH) induced insulin resistance representing the most significant underlying mechanism.

Aim: We present a comprehensive case report detailing the clinical findings and advanced hybrid closed-loop (AHCL) system data of a female patient with Type 1 diabetes mellitus diagnosed with GH-secreting pituitary adenoma.

Case description: 41-year-old female patient with Type 1 diabetes mellitus diagnosed at the age of 13, treated previously with intensified conventional therapy (ICT), was initiated continuous glucose monitor at the age 39 due to poor glycemic control (HbA1C 9.1%), despite adequate dietary compliance and close to normal weight (BMI 25.7 kg/m²). Initially, small improvement in her glycemic control was achieved (insulin need decreased from 0.93 to 0.73 U/kg/day). Throughout one-year glycemic control worsened (insulin need increased to 0.9 U/kg/day, time in range (TIR) decreased from 59 to 40%), and the patient was diagnosed with hypertension. The decision to transition to AHCL system was made, which despite improving glycemic control (TIR:68%), could not decrease insulin need (0.81 U/kg/day). The suspicion of GH-induced insulin resistance, raised based on slight clinical features, was confirmed by elevated level of IGF-1 (784.00 mg/l). Hormonal panel showed intact adrenal, thyroid and gonadal axes and normal prolactin level. GH suppression test using glucose was omitted, instead, GH profiling in an euglycemic state was performed with 2-hour interval measurements for 8 hours that revealed an elevated average GH level of 56,6 mg/l. A pituitary MRI showed a macroadenoma (16x15x14 mm), with a slight protrusion in the left sinus cavernosus (Knosp grade 2). Echocardiography, abdominal ultrasound and colonoscopy revealed no abnormalities. The patient was started on somatostatin analogue therapy and successful pituitary surgery was performed. Pathological examination showed mammosomatotroph pituitary neuroendocrine adenoma with elevated proliferation rate (Ki-67 index 5%). Postoperative GH and IGF-1 levels decreased and glycemic control improved (insulin need decreased: 0,55 U/kg/day, TIR: 73% and HbA1C: 7,5%).

Conclusion: The diagnosis of acromegaly in patients with Type 1 diabetes can often be challenging, early recognition of decreased insulin sensitivity in a previously well-controlled patient and characteristic clinical features are essential for accurate and timely diagnosis.