steroid hormones
Last reviewed 01/2018
Steroid hormones are not stored but are rapidly synthesised when required.
Tissues which produce steroid hormones include:
- ovary/testis
- adrenal cortex
- placenta
- skin (vitamin D)
All steroid hormones, including sex steroids, corticosteroids and vitamin D are based on the precursor molecule cholesterol. The synthetic pathways include multiple enzyme-dependent steps.
Steroid hormones tend to circulate at higher concentrations than peptide hormones, however, they are highly protein bound in plasma. Protein binding prevents rapid fluctuations in hormone concentrations and slows turnover.
For example, cortisol binds strongly to a plasma protein called cortisol binding globulin (CBG). When CBG is saturated, albumin is able to provide additional binding capacity.
Steroid hormones diffuse into cells and combine with cytoplasmic receptors. Receptor-steroid complexes then enter the nucleus where they regulate gene activity by binding DNA.