Nature of science:

Cooperation and collaboration between groups of scientists—the International Council for the Control of Iodine Deficiency Disorders includes a number of scientists who work to eliminate the harm done by iodine deficiency. (4.3)

• Endocrine glands secrete hormones directly into the bloodstream.
• Steroid hormones bind to receptor proteins in the cytoplasm of the target cell to form a receptor–hormone complex.
• The receptor–hormone complex promotes the transcription of specific genes.
• Peptide hormones bind to receptors in the plasma membrane of the target cell.
• Binding of hormones to membrane receptors activates a cascade mediated by a second messenger inside the cell.
• The hypothalamus controls hormone secretion by the anterior and posterior lobes of the pituitary gland.
• Hormones secreted by the pituitary control growth, developmental changes, reproduction and homeostasis.

Applications and skills:

• Application: Some athletes take growth hormones to build muscles.
• Application: Control of milk secretion by oxytocin and prolactin.

• Aim 8: There are numerous drugs that can enhance performance. Is the use of these drugs acceptable in terms of conducting a fair test as long as all athletes have equal access to them?