Endocrine Abstracts

Background: Thyroid hormones may affect bone calcium metabolism either by a direct action on osteoclasts or by acting on osteoblasts which mediate osteoclastic bone resorption. Hyperthyroidism induces an accelerated bone loss, causing hypercalcemia and may thereby increase the risk of low energy fractures. Increased IL-6 levels and hyperadrenergic state due to thyrotoxicosis, are also implicated in hypercalcemia.

Case: A 33 year old who is a known case of Graves’ thyrotoxicosis presented to the accident and emergency because of poor control of her thyrotoxicosis symptoms and previous history of asthma, for which she is on Propranalol (40 mg BD) and Carbimazole (10 mg OD). Thyroid examination revealed nodular goitre more enlarged on the right side and fine tremors were present in both hands, bilateral pedal oedema. Bloods revealed deranged thyroid and function test and liver function: TSH: <0.01 mU/l, FT4: >100 pmol/l, FT3: 49.4 pmol/l, calcium: 2.84 mmol/l, ALT 36.3 IU/l.

Patient suffered with constant nausea, poor appetite, weakness, myalgia, mood changes and many other symptoms indicative of poor control. So her Carbimazole dosage was stepped up to 30 mg OD and she was put on a short course of Prednisolone to counteract the impending thyroid storm. Her blood tests 6 weeks after this showed: TSH:<0.01 mU/l, FT4: 26.6 pmol/l, FT3: 9.5 pmol/l, with normal calcium: 2.53 mmol/l and normal ALT 17 IU/l.

Discussion: It has been reported that hyperthyroidism is associated with mild to moderate hypercalcemia in approximately 20% of total patients. The serum calcium levels are often increased by mild to moderate range and it rarely exceeds 3.0 mmol/l in hyperthyroidism associated hypercalcemia. The case presented here demonstrates the importance of timely control of calcium level by adequate anti thyroid treatment which was critical. A follow up appointment has also been arranged for her prior to which certain blood tests like Serum PTH and Vitamin D have also been requested in addition to the routine blood tests. However the quick normalisation of calcium level in her blood following optimisation of her anti thyroid treatment points towards thyrotoxicosis as the cause.

Conclusion: Though this is a rare case, clinicians should be aware of the association of hypercalcemia with hyperthyroidism because timely treatment can save the lives of patients and it should not be ignored after ruling out the other causes of hypercalcemia.