Which of the following is a secreted protein? Actin Tubulin Estrogen Growth hormone

The secreted protein among the options given is the Growth hormone.

Here's why:

1. Actin and Tubulin: These are not secreted proteins. They are intracellular proteins that play a crucial role in maintaining the cell's shape and function. Actin is involved in various cellular functions, including muscle contraction, cell motility, and cell division. Tubulin, on the other hand, is a major component of the cytoskeleton, providing structure and shape to the cells.

2. Estrogen: This is a steroid hormone, not a protein. It is involved in the regulation of the menstrual cycle and reproductive system in females.

3. Growth hormone: This is a secreted protein. It is produced and secreted by the pituitary gland and plays a significant role in growth, metabolism, and body composition. It is secreted into the bloodstream, which fits the definition of a secreted protein.