Additional worked examples

Worked example 11 (reading symptoms).

• A patient has a fasting blood glucose of 260 mg/100 cm³, passes a large volume of urine which tastes sweet, and drinks heavily.
• The cause is insulin deficiency (diabetes mellitus): glucose cannot enter cells, so blood glucose rises above the kidney threshold, glucose appears in urine and takes water with it.
• The patient is treated with insulin.

Worked example 12 (cause and effect chain).

• A woman with a tumour of the adrenal cortex develops a deep voice and facial hair.
• Explain: the tumour secretes too much androgen-like sex hormone, causing masculinisation; the excess hormone also inhibits the pituitary's gonadotrophins, so the ovaries shrink (atrophy).

Worked example 13 (comparing two diseases that have similar names).

• Diabetes mellitus — insulin deficiency, high blood glucose, glucose in urine.
• Diabetes insipidus — ADH deficiency, large volume of dilute urine, no excess glucose.
• Both cause great thirst.

Worked example 14 (experimental reasoning).

• A tadpole fed with thyroid extract metamorphoses into a tiny frog early; a tadpole whose thyroid is removed remains a tadpole.
• Conclusion: thyroxine controls metamorphosis and growth (thyroxine stimulates metabolism).