1. Symptoms

“Can I help you?” The indifferent voice crackled through the hospital intercom. “Please, I am so, so thirsty,” answered the young woman in the bed. “I feel awful, but I know I’d feel better if I could just have a drink of water.” Her mouth was so dry it hurt, and her head pounded painfully. She felt dizzy and sweaty.

“I’ll let your nurse know,” replied the voice.

It seemed to the woman that her life had always revolved around water. She was always thirsty, always drinking. When she went out, she carried two or three water bottles with her. When she went to sleep, she needed two glasses of water at her bedside. That morning she had come to the hospital for a C-section to deliver a baby too big to get out any other way. Now the beautiful baby was sleeping, and the mother was desperately thirsty. When the nurse appeared with a pitcher of water, the woman almost wept with relief.

The next morning, Dr. Heidi Chen, the OB-GYN intern, woke the patient early. The young doctor was worried, and it showed on her face. The patient had drunk an enormous amount of water in the hours following her C-section — well over three gallons. Her urine output had been just as remarkable. The doctor needed to figure out what was going on.

The patient sat up and rubbed her eyes sleepily. She was 38 years old, perfectly healthy and, she told Chen, she’d always liked to drink a lot of water. Her friends had sometimes kidded her about her constant array of water bottles and her frequent trips to the bathroom, but she’d never thought much about it. Her mother-in-law had been concerned, though. A few years earlier, when the woman and her husband were visiting his mother, something had gone wrong with their well, and they’d loaded up on bottled drinking water. That night the woman went to bed with a gallon bottle. The next morning it was empty. The surprised, then worried look on her mother-in-law’s face when she saw how much the young woman had drunk scared her a little.