Hypothyroidism associated with mixed connective tissue disease and its response to steroid therapy.

The case is reported of a 49-year-old housewife who presented with arthralgia and severe Raynaud's phenomenon. A diagnosis of mixed connective tissue disease (MCTD) was made on the basis of the clinical picture and serological findings. During the course of her disease she developed hypothyroidism. She was started on prednisolone to control the symptoms of the MCTD, and after this her thyroid function returned to normal despite her never having had any thyroid replacement therapy. There is reported evidence that Hashimoto's thyroiditis responds to systemic steroid preparations, but we can find no report of hypothyroidism in MCTD having a similar response.