Chapter 45, Problem 9TYU

Summary Introduction

To propose a hypothesis: How steroid and thyroid hormone receptor encode genes that evolved.

Concept introduction:

Endocrine cells secrete hormones into the extracellular fluids, which are signaling molecules. The secreted hormones reach target cells through the bloodstream. Hormones bind only to specific cells based on the corresponding receptors and they act through the chemical signals. They maintain homeostasis and regulate growth, development, blood pressure, metabolism and fluid concentration in the body.

Both thyroid and steroid hormones are lipid soluble hormones, they can diffuse plasma membrane and bind to transport proteins inside the cells and also they bind to the cytoplasmic receptors. Both the receptors have structural similarities and they are from nuclear receptor “superfamily” of proteins. The steroid/thyroid receptor isoforms may be evolved from the same gene by post-translational modifications or splicing.