Main articles: Growth hormone 1 and Growth hormone 2. Genes for human growth hormone, known as growth hormone 1 (somatotropin) and growth hormone 2, are localized in the q22-24 region of chromosome 17 and are closely related to human chorionic somatomammotropin (also known as placental lactogen) genes.
Average costs are U-shaped, and the marginal cost curve intersects the average cost curves at their respective minimum points. In the competitive model of the firm, the minimum average variable cost is termed the shutdown point because a firm will not produce in the short run if price is below average variable cost.
However, because the marginal cost curve is a plot of the slope of the total cost curve, then the shape of the total cost curve also reflects the law of diminishing marginal returns. The flattening slope of the total cost curve for small quantities of output is due to increasing marginal returns.