Case
A 37-year-old Caucasian male was referred with 20kg unintentional weight loss, multiple vertebral fractures and osteoporosis on DEXA. Thoraco-lumbar x-ray revealed morphometric fractures of T10/T11/T12/L1 and CT lumbar spine showed additional crush fractures at L3/L4. Z-scores at the lumbar spine and left femoral neck were -3.0 and -2.9 respectively, suggesting an underlying pathological cause.
Secondary screening revealed florid Graves’ disease (TSH <0.05mU/L, T4 61pmol/L, T3 28.9pmol/L), with markedly elevated thyroid stimulating immunoglobulin 110U/L (200x upper limit of normal). Surprisingly his symptom burden was mild, and there were no features of Graves’ orbitopathy or dermopathy. He was commenced on carbimazole 15mg tds.
He was vitamin D replete with adequate dietary calcium intake. The remainder of his secondary osteoporosis screen was unremarkable. His only other risk factor for osteoporosis was smoking (~20 pack-year history) and there was no family history of premature osteoporosis/fracture.
Six months later he had an exacerbation of back pain with a new L2 vertebral fracture, despite achieving near biochemical euthyroidism. He remains on carbimazole 15mg bd and definitive management has been discussed.
Denosumab was inadvertently commenced by his GP in-between clinic visits. Ongoing management options include antithyroid medication alone, transitioning to bisphosphonate therapy or an anabolic agent. DEXA is due to be repeated.
Discussion
Multiple vertebral fractures as the presenting feature of Graves’ disease in a young male is unusual. Whilst bone loss (cortical>trabecular) is a uniform feature of overt hyperthyroidism, studies examining the impact of Graves’ disease on BMD and vertebral fractures in men are scarce, especially in younger populations1,2.
Furthermore, studies examining reversibility of bone loss with treatment of hyperthyroidism have yielded variable results, and have largely focused on post-menopausal women. Additional studies are required to evaluate the impact of antithyroid medication and/or antiresorptive therapy in young males with Graves’ disease to further inform management.