1. Chemical Pathology & Metabolic Medicine; Department of Clinical Biochemistry; Addenbrooke's Hospital; Hills Road; Cambridge; CB2 0QQ; UK
2. Department of Endocrinology; Lister Hospital; Corey's Mill Lane; Stevenage SG1 4AB and Department of Investigative Sciences; Imperial College; London; UK
3. Department of Endocrinology; Lister Hospital; Corey's Mill Lane; Stevenage SG1 4AB; UK