Q18 - Untangling GH and IGF1 Roles in Growth-Plate Elongation

Theoretical A Real exam question - full text reproduced under IBO's CC BY-NC-SA 4.0 license

Growth hormone (GH) is secreted by the brain, and can stimulate the liver to secrete insulin-like growth factor 1 (IGF1). Bones, formed from chondrocytes, elongate from terminal growth plates as animals grow. (1) A healthy, active growth plate. All the growth plates injected with GH activated. (2) GH was injected into rat growth plates in combination with IGF1 inhibitors. (3) All GH was inhibited in a rat. (4) GH injected into a rat growth plate with a liver specific IGF1 knockout. (5) GH was added onto stem cells in a dish.

Figure for Q18: Untangling GH and IGF1 Roles in Growth-Plate Elongation

Using the information and data, determine which of the statements are true or which are false.

A. Mutations in GH can lead to dwarfism.

B. IGF1 is necessary for chondrocytes to enlarge.

C. Injecting IGF1 would lead to bone elongation, even if GH is absent.

D. IGF1 is produced by chondrocytes, as well as the liver.

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Question reproduced from IBO 2017, Theoretical Exam A, licensed under CC BY-NC-SA 4.0 - attributed to the International Biology Olympiad. Open the full exam PDF · Official answer key & worked solutions