Endocrine Abstracts

JOINT2105

Background: Graves’ disease is the most common etiology of hyperthyroidism which is a cause of secondary osteoporosis. Thyrotropin (TSH) is known to affect directly the bone metabolism through the TSH receptor and TSH receptor antibodies (TRAb) may have an important role in bone turn-over. This study aimed to determine the correlation between TRAb and bone remodeling markers (BRMs) in patients newly diagnosed with Graves’ disease.

Patients and methods: We performed a cross-sectional study at the endocrinology department of Charles Nicolle Hospital in Tunis, Tunisia including newly diagnosed patients with Graves’ disease from Juin to Decembre 2023. Subjects with co-morbidities (hyper or hypoparathyroidism, inflammatory bowel disease, malabsorptive disorder, renal disease, chronic liver disease, Cushing’s disease, hypogonadism), pregnant, breast-feeding or menopausal women or history of drug use (steroid, bisphosphonates, calcium or vitamin D) were not included in the study. BRMs involving total alkaline phosphatase (ALP), osteocalcin (OSC) and Carboxy-terminal telopeptide of type I collagen (CTX-I) were assessed in Clinical Biochemistry and Hormone Laboratory of Pateur Institute.

Results: Our study population consisted of 34 patients newly diagnosed with Graves’ disease with a higher prevalence of female subjects (76,5%). Mean age of participants was 38,5 ± 10,4 years. Mean level of free thyroxine (FT4) and TSH were respectively 3,5 ± 1,9 ng/dl [NR: 0,7–1,8 ng/dl] and 0,02 ± 0,01 mUI/l[NR: 0,4 – 4 mUI/L]. Mean level of TRAbs was 20,4 ± 12,6 UI/l[NR:<2UI/L]. Elevated levels of ALP, osteocalcin, and CTX-I were observed in 24,2 %, 42,4%, and 45,5 % of patients, respectively, based on laboratory reference ranges. TRAb levels were positively and significatively correlated to PAL (P = 0,01) and osteocalcin (P = 0,03). Although TRAb levels vary in the same direction as CTX levels, this association wasn’t significant (P >0,05). Receiver operating characteristic (ROC) analysis identified a significant TRAb cut-off value for predicting elevated ALP and osteocalcin levels. The ROC-determined cut-off was 44 UI/l, with a sensitivity of 66.7% and a specificity of 87.5% for predicting elevated ALP. The same cut-off value predicted elevated osteocalcin with a sensitivity of 83.3% and a specificity of 44.4%.

Discussion and Conclusion: This study reveals a positive correlation between TRAb and BRMs in patients newly diagnosed with Graves’ disease. This suggests a detrimental impact of TRAb on bone metabolism in the context of hyperthyroidism. Importantly, normalization of the autoimmune abnormality occurs significantly later than the restoration of euthyroidism, with TRAb levels gradually disappearing over an extended period.