What is the Origin of Tissue Hormone Uptake?

This term is derived from cell biology and pharmacokinetics, focusing on the distribution phase of hormone action. It acknowledges that the concentration of hormone in the serum does not perfectly reflect the concentration at the site of action within the cell. The concept highlights the importance of peripheral tissue health in mediating hormonal benefits.

What is the Mechanism of Tissue Hormone Uptake?

For lipophilic steroid hormones, uptake primarily occurs via passive diffusion across the cell membrane, driven by the concentration gradient of the free hormone. However, membrane transporters and the rapid dissociation from albumin also facilitate this process. Once inside the cell, the hormone binds to its intracellular receptor, initiating the cellular androgenic response. The rate of uptake is further modulated by the local blood flow and the expression levels of tissue-specific hormone metabolizing enzymes.

Tissue Hormone Uptake ∞ Area

Tissue Hormone Uptake

Meaning

Tissue hormone uptake refers to the process by which circulating hormones, particularly the free and bioavailable fractions, are transported from the bloodstream across the capillary endothelium and cellular membranes into the target tissues where they exert their biological effects. The efficiency of this uptake is a critical determinant of hormone action, often being regulated by local tissue factors, receptor density, and blood flow. This process is the final, essential step in the endocrine signaling pathway.