ODP320 Immune Organs Enlarged in Acromegaly: Evaluation of Thymus Volume in Patients with Acromegaly

OBJECTIVES: The thymus is an important immunological organ where T cell maturation takes place, especially in the early stages of life. Animal studies have shown that the structure and functions of the thymus are controlled by hormones. Growth hormone (GH) and insulin-like growth factor-1 (IGF-1) stimulate both thymic epithelial cells and thymocytes. This causes an increase in the number of cells and the secretion of cytokines. These effects of GH and IGF-1 on the thymus have not yet been confirmed in humans. We have hypothesized that, acromegaly with chronic GH and IGF-1 elevation, may change the volume and the functions of the thymus. In this study, we have examined the thymus volume in patients with acromegaly. MATERIALS AND METHODS: In this single center study, 393 patients with acromegaly were retrospectively evaluated to identify patients who underwent chest CT for any reason before and/or after pituitary surgery. Since 64 patients in the acromegaly group had chest CT, we also selected 64 patients as an age- and sex-matched control group among trauma patients without any known disease who admitted to the emergency department. All chest CT images were reassessed by a radiologist to detect the thymus gland and calculate its volume (if visible) who was unaware of clinical data. The frequencies and volumes of visible thymus glands were compared between acromegaly and control groups. RESULTS: Mean (±SD) age was 49.9±13.8 years in acromegaly group and 51.7±14.1 years in control group(p= 0.32). Twenty-seven patients (42.2%) from each group were female. Median (IQR) GH levels were 10. 0 (21.1) ng/mL and mean±SD IGF-1 levels were 729.5±283.5 ng/mL. While 51 patients (79.7%) had a visible thymus gland at chest CT in acromegaly group, only 29 patients (45.3%) had a visible thymus gland in control group (p<0. 001). Median (IQR) values for the volumes of visible thymus glands in acromegaly and control groups were 13. 0 (9.4) cm 3 and 10.3 (7.6) cm 3, respectively (p=0. 014). There was no correlation between thymus gland volume and GH(r=-0. 02; p= 0.91) and IGF-1(r=0.11; p=0.49) levels. In acromegaly group, six patients had a visible thymus gland on both preoperative and postoperative chest CTs. After surgery, hormonal remission was achieved in four patients and thymus gland volume decreased in three of them (Patient 1: 15.26 to 17.23, Patient 2: 22.66 to 15.88, Patient 3: 19. 00 to 11.80 and Patient 4: 17.78 to 12. 07 cm 3). Volume increase was observed in two uncontrolled patients (Patients 5: 12.45 to 15.42, Patient 6: 6. 05 to 19.59 cm 3). CONCLUSION: This study has firstly shown that, the thymus is enlarged in patients with acromegaly. Effective control of the disease reduces thymus volume. Further research is needed to elucidate this association and its putative clinical implications. Presentation: No date and time listed