Hip Structure Analyses in Acromegaly: Decrease of Cortical Bone Thickness After Treatment: A Longitudinal Cohort Study

Abstract

Long‐standing growth hormone (GH) excess causes the skeletal clinical signs of acromegaly with typical changes in bone geometry, including increased cortical bone thickness (CBT). However, a high prevalence and incidence of vertebral fractures has been reported. The aim of this study was to assess the course of cortical bone dimensions in the hip by comparing patients with acromegaly and clinically nonfunctioning pituitary adenomas (NFPAs) at baseline and 1 year after pituitary surgery (1‐year PO) in a longitudinal cohort study. DXA was performed in patients with acromegaly (n = 56) and NFPA (n = 47). CBT in the femoral neck (CBTneck), calcar (CBTcalcar), and shaft (CBTshaft) were determined by hip structural analysis (HSA). CBT at baseline and the change to 1‐year PO were compared. Test results were adjusted for differences in gender distribution, age, and gonadal status. Cortical thickness analyses showed higher values [mm] at baseline in patients with acromegaly compared with NFPA: CBTneck median [25th; 75th] 6.2 [4.7; 8.0] versus 5.1 [4.1; 6.4] (p = 0.006), CBTcalcar 4.8 [4.2, 5.7] versus 4.0 [3.2, 4.5] (p < 0.001), CBTshaft 6.2 [5.1, 7.2] versus 5.2 [4.6, 6.0], (p = 0.003). In acromegaly, GH was correlated with CBTneck (r = 0.31, p = 0.020), whereas IGF‐1 was correlated with CBTcalcar (r = 0.39, p = 0.003) at baseline. In acromegaly, CBTneck decreased by 11.2%, p = 0.002 during follow‐up. Finally, the decrease in CBTneck and CBTcalcar in acromegaly was significant compared with NFPA (p = 0.023 and p = 0.017, respectively). Previous observations of increased CBT in acromegaly were confirmed with DXA‐derived HSA in a large, well‐defined cohort. The decline in CBT in acromegaly could contribute to the increased fracture risk in acromegaly despite increased bone dimensions and disease control. © 2019 The Authors. JBMR Plus published by Wiley Periodicals, Inc. on behalf of American Society for Bone and Mineral Research.

Endocortical Trabecularization in Acromegaly: The Cause for the Paradoxically Increased Vertebral Fracture Risk?

“…(2) Moreover, cortical thickness by HSA was increased in acromegaly compared with the NFPA patients and changed differently by group during 1 year of follow-up in the hip region. (20) These data were further developed in the present study. The CBT analyses were in general not dependent on sex or gonadal status in the hip region (CBT neck and CBT calcar) but lower in females in the shaft region, reflecting the women's smaller body dimensions.…”

“…(5,17) Based on bone mineral density (BMD) measurements of the hip (TH) and femoral neck (FN) by dual X-ray absorptiometry (DXA), structural information can be derived (hip structure analysis [HSA]) (18,19) and be of importance for understanding the biomechanical competence of the appendicular skeleton and the interplay between the different envelopes in acromegaly. (20) Whereas BMD by DXA gives a quantitative assessment of the investigated region (ex the lumbar spine [LS]), trabecular bone score (TBS) provides an estimation of bone microarchitecture, potentially reflecting the biomechanical properties of trabecular bone. (21,22) As reviewed recently, studies of TBS in acromegaly have shown inconsistent results.…”

Increased Risk of Hip Fracture in Patients with Acromegaly: A Nationwide Cohort Study in Korea

“…The study showed higher total hip and femoral neck cortical thickness and lower lumbar areal bone mineral density (BMD), trabecular bone score, and total hip trabecular volumetric BMD in patients with acromegaly than in healthy controls [ 21 ]. Another study showed an increase in femoral cortical bone thickness and an enlargement in bone diameter in patients with active acromegaly due to the prominent effect of periosteal bone formation [ 22 ]. Then, after 1 year of pituitary surgery, the femoral cortical bone thickness decreased with unchanged bone dimension, and this unbalanced geometry may consequently lead to inferior mechanical properties of the hip in patients with acromegaly [ 22 ].…”

“…Another study showed an increase in femoral cortical bone thickness and an enlargement in bone diameter in patients with active acromegaly due to the prominent effect of periosteal bone formation [ 22 ]. Then, after 1 year of pituitary surgery, the femoral cortical bone thickness decreased with unchanged bone dimension, and this unbalanced geometry may consequently lead to inferior mechanical properties of the hip in patients with acromegaly [ 22 ]. Additionally, after GH-lowering treatments, endocortical bone resorption becomes more prominent than periosteal bone formation, similar to normal aging, leading to decreased cortical bone thickness [ 22 ].…”

“…Then, after 1 year of pituitary surgery, the femoral cortical bone thickness decreased with unchanged bone dimension, and this unbalanced geometry may consequently lead to inferior mechanical properties of the hip in patients with acromegaly [ 22 ]. Additionally, after GH-lowering treatments, endocortical bone resorption becomes more prominent than periosteal bone formation, similar to normal aging, leading to decreased cortical bone thickness [ 22 ]. Altogether, during the active phase of acromegaly, the trabecular bone is mainly damaged, and the cortical bone compensates for it [ 21 , 22 ].…”