Oestradiol and progesterone act through intracellular receptors to regulate gene expression and coordinate reproductive tissue changes, linking signal detection to a specific target-cell response.
Oestradiol and progesterone are steroid hormones whose effects depend on intracellular receptors in specific target cells.
For oestradiol, the required target is receptor-containing cells in the hypothalamus that secrete gonadotropin-releasing hormone (GnRH). Oestradiol changes gene expression and thereby influences GnRH secretion.
For progesterone, the required target is receptor-containing cells in the endometrium. Progesterone-dependent gene expression maintains the endometrium in a state that can support pregnancy.
The same circulating hormone affects only cells with the matching receptor: hypothalamic GnRH-secreting cells respond to oestradiol, whereas endometrial cells are a specified target of progesterone.
Do not generalize these objectives to every reproductive effect of the hormones. The assessed target-cell examples are oestradiol in GnRH-secreting hypothalamic cells and progesterone in endometrium.
A ligand only affects target cells with the matching receptor. Quorum sensing uses autoinducers and thresholds for group behaviour. Animal signals differ by source, distance, speed, target-cell response, and chemical class. Hydrophilic ligands use transmembrane receptors and relays; steroid and thyroid hormones use intracellular receptors that affect transcription. Named pathways then show the logic: acetylcholine opens sodium channels, GPCRs switch G proteins through GDP-GTP exchange, epinephrine uses cAMP and kinase cascades, insulin RTKs use dimerisation/autophosphorylation to move GLUT4 and promote glycogenesis, steroid hormones change gene expression, and feedback either amplifies or restores stability.