Patients with acromegaly experience various systemic complications due to prolonged exposure of tissues to high levels of GH and IGF-1. This excess leads to significant changes in bone quality, structure, and strength, characterized by increased bone formation and resorption, with a predominance of the latter, as well as altered calcium metabolism. Consequently, there is a decline in bone microarchitecture and an elevated risk of fractures, particularly vertebral fractures, even in patients with normal bone mineral density (BMD).
Our study found a considerably high prevalence of fragility fractures among patients with acromegaly, independent of age, sex, BMI, time of evolution of acromegaly, IGF-1 levels at the time of diagnosis, and the control of the disease. However, a significant difference was observed between patients treated with somatostatin analogs. According to our findings, somatostatin analog therapy was positively correlated with the presence of osteoporosis.
Multiple studies have demonstrated that acromegaly has profound effects on the quality of the hip bone, causing impaired trabecular bone formation and increased cortical thickness. Consequently, these changes lead to alterations in the bone structure of the hip [15–17]. The majority of studies have focused on the risk of vertebral fractures, while few have investigated hip and non-vertebral fractures, as well as the risk factors for these fractures, in patients with acromegaly. A recent study found that patients with acromegaly have an increased risk of hip fractures, which is even higher than the risk of clinically apparent vertebral fractures [23]. We observed a high prevalence of non-vertebral fragility fractures, including hip fractures, along with a decreased femoral neck BMD. It is crucial to ascertain the prevalence and risk factors for hip and non-vertebral fractures in the population with acromegaly. However, the limited sample size poses challenges in conducting comprehensive analyses in this regard. Further studies are needed to evaluate the prevalence and risk factors for hip and non-vertebral fractures in this patient group.
Regarding vertebral fractures acromegaly was once considered a potential bone neutral or even protective factor against fractures by increasing bone formation [26, 27]. Nevertheless, multiple studies have subsequently shown a high prevalence of vertebral fractures in patient with acromegaly, with prevalence rates ranging from 10% to more than 50% in certain patients [25–29]. There was a low prevalence of vertebral fractures compared to previous studies, likely because clinically or radiologically diagnosed vertebral fractures were included, but without a systematic and active search using a specific imaging technique.
A limitation in the diagnosis of vertebral fractures in clinical practice includes the lack of a satisfactory gold standard criteria for its diagnosis. While morphometric assessment from radiographs seems to be the most accepted, magnetic resonance imaging has shown good accuracy. The use of conventional radiography can lead to a lack of vertebral fracture diagnoses in several patients. Additionally, morphometry assessment of radiographic images needs a trained radiologist to avoid misdiagnosing vertebral fractures as vertebral deformities frequently found in patients with osteoporosis [33, 39–44].
Our study revealed a significant correlation between the treatment with somatostatin analogs and the occurrence of osteoporosis, but did not find a significant correlation with fragility fractures. Chiloiro et al's study suggests a possible higher risk of vertebral fractures in patients treated with pegvisomant compared to pasireotide [45]. Our findings indicate that the severity of the disease and the need for second-line therapies, rather than a specific medication for acromegaly, may be associated with the increased risk of osteoporosis. However, it is important to note that despite the description of somatostatin receptors in rodent bone since the 1990s, limited research has been conducted on somatostatin receptors and the effect of somatostatin analogs on bone. A recent study has demonstrated that octreotide may have a direct effect on bone by inhibiting osteoblast proliferation and promoting apoptosis [46, 47].
Regarding additional risk factors for osteoporosis and fractures, patients with acromegaly often have multiple risk factors such as glucocorticoid use for secondary adrenal insufficiency, type 2 diabetes mellitus, and hypogonadism. Patients with type 2 diabetes mellitus, hypogonadism, and glucocorticoid users have a higher risk of vertebral fractures, which, in some cases, is independent of BMD impairment. [7, 18–22]. A large proportion of patients with acromegaly exhibit hypogonadism either due to GH excess or acromegaly treatment, especially after pituitary radiation [29]. It is crucial to consider that type 2 diabetes mellitus, hypogonadism, and glucocorticoid use can have a negative impact on trabecular bone and serve as risk factors for reduced bone mineral density (BMD) and an elevated risk of fractures, particularly vertebral fractures. Our study revealed a high prevalence of comorbidities associated with higher prevalence of osteoporosis and fractures. Type 2 diabetes, hypogonadism, and adrenal insufficiency were found in 23%, 9%, and 16% of patients, respectively. This indicates that more than half of the patients have significant risk factors for vertebral fractures and osteoporosis. Therefore, the impairment of femoral neck bone mineral density (BMD) and the presence of non-vertebral fractures, as indicators of cortical bone involvement, may serve as potential risk factors for future fractures in patients with acromegaly.
This study has certain limitations. Due to its observational nature, we were unable to establish a causal relationship between acromegaly, osteoporosis, and fractures. Our results were based on clinical records and depended on the availability of data registered in the patients records and images available from the insurer. None of the patients underwent systematic screening for osteoporosis and fractures, and there was heterogeneity in the type of imaging performed with variable sensitivities and specificities.