Poster Abstract Abstract

(Adults - Thyroid), #220531485066

Concomitant Graves’ Disease and Myasthenia Gravis: Improvement In Thyroid Profile After Thymectomy

Fatimah Zaherah Mohamed Shah, Endocrine Unit, Universiti Teknologi MARA; Aimi Fadilah Mohamed, Endocrine Unit, Universiti Teknologi MARA; Sharifah Faradilla WM Hatta, Endocrine Unit, Universiti Teknologi MARA; Nor Aisyah Zanordin, Endocrine Unit, Universiti Teknologi MARA; Nur Aini Eddy Warman, Endocrine Unit, Universiti Teknologi MARA; Mohd Hazriq Awang, Endocrine Unit, Universiti Teknologi MARA; Rohana Abdul Ghani, Endocrine Unit, Universiti Teknologi MARA

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There is a known association between autoimmune thyroid disease and myasthenia gravis (MG) with shared autoimmunity, and treatment of one condition can affect the other. We describe an interesting case where thymectomy resulted in better thyroid hormone profile


A 14-year-old-girl was diagnosed with Graves’ disease when she presented with irritability, insomnia and ophthalmopathy with a diffuse goiter, and started on treatment. She had minimal improvement of her symptoms, with persistent subclinical hyperthyroidism. A year later she had worsening muscle weakness with diplopia and fatiguability. Diagnosis of MG was confirmed with positive anti-cholinesterase-antibody and thymoma on the CT Thorax. Treatment with pyridostigmine improved myopathy and diplopia temporarily.


She underwent radioactive-iodine (RAI) therapy with 15MCi due to persistent biochemical hyperthyroidism with mood disturbances and intermittent muscle weakness, 18 months after treatment of hyperthyroidism, and became hypothyroid within 5 months. Following initiation of L-thyroxine and normalization of her thyroid function, her myasthenia also improved with pyridostigmine stopped for a year. However, she developed persistent hypothyroidism a few months later with worsening constipation and depression with suicidal ideation even with increasing doses of thyroxine. A year after stopping pyridostigmine, she had a flare of MG necessitating recommencement with increasing doses of pyridostigmine. However, with worsening constipation and difficulty in controlling both her hypothyroid and myasthenic state attributed to reduced absorption of medication, she underwent thymectomy 4 years after diagnosis of MG. Following thymectomy, her myasthenia improved markedly, with reduction in constipation and subsequent improvement in control of her hypothyroid state.


We illustrate a case of concomitant autoimmune thyroid disease and MG, describing both the ‘see-saw’ and reverse ‘see-saw’ relationship. Interestingly, treating MG with thymectomy resulted in better control of post-RAI hypothyroidism, postulated due to improvement in gut motility and hence absorption of medication.

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