Assessment Practice
Clinical Case Studies
Diabetes insipidus
Look at each of these clinical case studies and answer the questions
Case Study 1. Jack.
Diagnosing
- Jack - a scaffolding contractor - visited his GP worried about his high rate of urination per day (up to 20 litres) and his constant raging thirst.
- His GP suspected Jack was deficient in a peptide pituitary hormone responsible for regulating water retention by the kidneys.
- The question was, why had Jack suddenly developed this condition?
- The GP noticed a work related injury some months ago recorded in Jack's medical notes. While supervising a contract Jack had been struck on the skull by a heavy scaffold clip falling from the upper floor of one of his contracts. Although wearing a safety helmet he had suffered a fracture of the base of the skull and was still off work.
- The GP then made the connection between the hormone and the injury and diagnosed a condition called Diabetes insipidus.(DI)
- This was confirmed by a hospital consultant following tests.
Jack's Treatment.
- Patients with this form of DI are prescribed a medicine called desmopressin which is similar to the peptide hormone they are deficient in. Modern forms may be available as tablets, nasal spray or injection.
- The chemical structure of the hormone (and desmopressin) means that only small amounts of the tablet form of the hormone actually get into the bloodstream via the gut.
- This was the case with Jack, so he now self-administers the drug using a nasal spray-quick, easy and for him, effective.
Clinical questions:
- Name the peptide hormone Jack's GP suspected he was deficient in.
- Name the precise part of the kidney nephron where this hormone acts.
- What process takes place in this part of the nephron?
- How does the hormone act on this structure?
- Why should Jack's accident at work have resulted in the hormone deficiency?
- Explain why "the chemical structure of the hormone" limits its usefulness for some individuals.
- Why might a nasal spray be "quick"?