Endocrine Abstracts

Introduction: Myotonic dystrophy type 1 (DMT1) is the most prevalent muscular dystrophy that affects 1 in 8000 individuals. Disease is caused by CTG repeat expansion of the DMPK gene located on chromosome 19. Beside neuromuscular involvement, studies have found an increased prevalence of endocrinopathies such as diabetes, hyperparathyroidism and hypogonadism. The exact underlying mechanism of endocrine dysfunction remains unclear. Moreover, endocrine dysfunction is progressive in nature as is the muscle affection. We illustrate the problem with following clinical case.

Case report: 47-year old women, complaining of chronic fatigue, muscle weakness and anxiety was admitted to our department for an evaluation of low TSH, T4, T3, hypercalcemia, hypophosphatemia, and elevated PTH level. We performed pituitary MRI, neck ultrasound, ^99mTc sestamibi SPECT/CT and all results were unremarkable. Other pituitary hormone testing showed normal findings. We diagnosed patient with secondary hypothyroidism and primary hyperparathyroidism, introduced levothyroxine along with hidration and furosemide and decided to do regular check-ups. However, patient was not feeling better with therapy. In the meantime, she underwent genetic testing for myotonic dystrophy type 1 as her son was diagnosed with severe form of disease after suffering cardiorespiratory insufficiency during influenza. Later on, her son developed primary adrenal insufficiency and primary hypogonadism. In further monitoring, our patient´s calcium and PTH levels where persistently elevated. Given the inability to locate hyperactive parathyroid tissue and an increased perioperative risk due to neurological disease itself, we decided to treat patient conservatively rather than surgically. Despite hidration, furosemide, pamidronate and cinecalcet, calcium levels did not decrease.¹⁸F choline PET/CT is not a routine diagnostic method for this indication in our country. We performed it for the first time in this patient and found 6 mm large hyperactive tissue in the projection of the left lobe of the thyroid gland. Patient underwent surgery and finally calcium, phosphorus and PTH levels normalized. Couple of years later we noticed elevation in fasting glucose and HbA1c levels, so we started metformin therapy. She is well now but we keep monitoring the rest of the endocrine function, especially adrenal function.

Conclusion: Myotonic dystrophy type 1 and associated endocrinopathies are one more proof of neuroendocrine connection. In all patients suffering from it, endocrine evaluation and monitoring is obligatory. Although Consensus-based Recommendations from Myotonic Dystrophy Fundation do not mention screening of the parathyroid gland function, it is one of the most common endocrinopathy and should be evaluated in these patients as well.