Myxedema Coma Induced by Ingestion of Raw Bok Choy

To the Editor:

An 88-year-old Chinese woman was brought to the emergency department by her family, who reported that she had been lethargic and unable to walk or swallow for 3 days. She had been eating an estimated 1.0 to 1.5 kg of raw bok choy daily for several months in the belief that it would help control her diabetes. She had no previous history of thyroid disease.

On examination the patient was lethargic. The temperature was 36.1°C, the pulse 58 beats per minute, blood pressure 181/89 mm Hg, and the respiratory rate 22 breaths per minute. A pulse oximetry reading was 92%. She had periorbital edema and macroglossia, and her thyroid was not palpable; she also had pitting edema in her lower legs. Her skin was dry and her hair was coarse; a neurologic examination revealed clonus and hyperreflexia in the right leg due to a previous stroke. The remainder of her examination was normal.

Laboratory testing was significant for serum levels of sodium (118 mmol per liter), thyrotropin (74.4 mIU per liter; 0.65 mIU per liter 4 months earlier; normal range, 0.4 to 4.0 mIU per liter), free thyroxine (undetectable; normal range, 0.7 to 2.2 ng per deciliter), and thyroid peroxidase antibodies (13 IU per milliliter; normal range, <20 IU per milliliter). The patient was intubated for hypoxemic and hypercarbic respiratory failure and admitted to the intensive care unit with a diagnosis of severe hypothyroidism with myxedema coma. She was treated with intravenous methylprednisolone and levothyroxine and was eventually discharged to a skilled nursing facility.

Brassica rapa chinensis, otherwise known as bok choy or Chinese white cabbage, contains glucosinolates, a group of compounds that occur widely in the genus. Some of the breakdown products of glucosinolates, such as thiocyanates, nitriles, and oxazolidines, have been implicated for their inhibitory effects on the thyroid. Studies in the 1920s were the first to note the development of hypertrophic goiters in rabbits that were mainly fed a diet of cabbage.¹ Interest in the possible goitrogenic properties of foodstuffs led to the discovery of 1,5-vinyl-2-thiooxazolidone in brassica seeds and in yellow turnips. The compound was termed a goitrin because it inhibited the uptake of iodine by the thyroid gland.² In our patient, the problem was her consumption of considerable amounts of raw bok choy. When eaten raw, brassica vegetables release the enzyme myrosinase, which accelerates the hydrolysis of glucosinolates; the cooking process largely deactivates the myrosinase in these vegetables.³ This case demonstrates the potential for nutritional factors to have a profound effect on health.

Michael Chu, M.D.
Terry F. Seltzer, M.D.
New York University School of Medicine, New York, NY
michael.[email protected]org