A 15-year-old boy with a 10-year history of type 1 diabetes mellitus was referred to the adolescent diabetes clinic from the paediatric clinic. Diabetes control had always been satisfactory and his recent haemoglobin A1c concentration was 67 mmol/mol (20C42). He felt generally well, although on a growth chart his weight had fallen steadily from the 50th centile 18 months previously to the 10th centile, and his height had fallen from the 50th centile to the 25th centile. He had stage 4 genital development and stage 4 pubic hair, and testicular volume was 15 mL.
What is the most appropriate investigation?
A . anti-tissue transglutaminase antibodies
B . insulin-like growth factor 1
C . serum testosterone
D . short tetracosactide (Synacthen®) test
E . thyroid-stimulating hormone and free thyroxine
Answer: A