Oxytocin and vasopressin/ADH (Posterior Pituitary Hormones) Physiology
A short physiology lesson on oxytocin and ADH (vasopressin), covering where they are made, what triggers them and how they act on the uterus, breast, kidney and blood vessels.
Key moments
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- 0:06Hypothalamus and posterior pituitaryHasudungan explains how the hypothalamus controls the pituitary and how magnocellular neurons run to the posterior pituitary to release peptides into the circulation.
- 1:08Oxytocin and ADH share an originHe names the two posterior pituitary hormones and says they are closely related because the same type of neuron produces both.
- 1:45Oxytocin and the labor feedback loopHe describes cervical stretch signaling the hypothalamus, oxytocin-driven uterine contractions and the positive feedback that continues until birth. He mentions clinical use of oxytocin analogs.
- 2:54Oxytocin and milk ejectionHe explains that suckling triggers oxytocin release, which contracts the cells around the breast lobules to eject milk.
- 3:47ADH function and the nephronHe introduces ADH as increasing water reabsorption in the distal nephron, then lists the segments of the nephron and what each does with water.
- 5:21What triggers ADH releaseHe says ADH is released when plasma osmolarity rises or blood volume falls, and that the hypothalamus responds more to small osmolarity changes.
- 6:52ADH action on principal cellsHe describes ADH binding V2 receptors, aquaporin 2 insertion on the apical surface and water leaving via aquaporin 3 and 4.
- 7:23Vasoconstriction through V1 receptorsHe says ADH also raises vascular resistance and blood pressure via V1 receptors, usually only in severe blood loss or infection.
What the video says
Armando Hasudungan gives a textbook-style explanation of the two hormones released from the posterior pituitary, oxytocin and antidiuretic hormone (ADH, also called arginine vasopressin). He starts by describing how magnocellular neurons run from the hypothalamus to the posterior pituitary, where both neuropeptides are released into the circulation. He presents them as closely related because they share this origin.
On oxytocin, he says it is expressed mainly in females around birth and breastfeeding. In labor, he explains, stretching of the cervix signals the hypothalamus to release more oxytocin, which acts on uterine receptors to cause rhythmic contractions, creating a positive feedback loop until delivery is complete. He notes that oxytocin analogs are sometimes used clinically during labor and delivery. For lactation, he describes how suckling prompts oxytocin release, which makes the cells surrounding the breast lobules contract and eject milk, another positive feedback loop.
The second half covers ADH. Hasudungan says its main job is to increase water reabsorption in the distal part of the nephron, with a secondary role in vasoconstriction. He walks through the parts of the nephron, states that the proximal tubule reabsorbs about 90% of filtered water, and attributes the remaining 10% mainly to ADH action on principal cells. He says ADH release is triggered by a rise in plasma osmolarity, which he equates roughly with sodium levels, or by a fall in blood volume, with the hypothalamus more sensitive to osmolarity.
He finishes with the cell-level mechanism. ADH binds V2 receptors on principal cells, causing aquaporin 2 channels to be inserted on the apical surface, and water exits through aquaporin 3 and 4 channels. He adds that ADH can also raise vascular resistance through V1 receptors, which he says usually happens only during severe blood loss or infection. The video is about normal physiology and does not discuss supplements or dosing.
On each compound
Oxytocin1:45
Hasudungan describes oxytocin as made by hypothalamic neurons and released from the posterior pituitary. He says it drives uterine contractions in labor and milk ejection during breastfeeding, each through a positive feedback loop, and that oxytocin analogs are sometimes used clinically during labor and delivery.
See how your DNA reads OxytocinWhat this video doesn’t settle
- It is a general physiology overview and does not cover oxytocin or vasopressin as supplements, doses, or side effects.
- It mentions clinical oxytocin analogs in labor in a single sentence without naming products, doses, or evidence.
- The lesson describes oxytocin mainly in childbirth and lactation and does not address other roles of the hormone.
Questions this video answers
What does oxytocin do in the body according to this video?
Hasudungan says oxytocin acts on uterine receptors to cause rhythmic contractions during labor and makes breast cells contract to eject milk during lactation. He describes both as positive feedback loops.
What is the difference between oxytocin and ADH?
Hasudungan says both are neuropeptides made by magnocellular neurons and released from the posterior pituitary. Oxytocin is tied to childbirth and milk ejection, while ADH mainly increases water reabsorption in the kidney and can also constrict blood vessels.
What triggers ADH release?
He says ADH is released when plasma osmolarity rises or blood volume drops, with the hypothalamus more sensitive to small osmolarity changes. He equates osmolarity roughly with blood sodium levels.
How does ADH make the kidney hold on to water?
According to Hasudungan, ADH binds V2 receptors on principal cells of the distal nephron and collecting duct. This inserts aquaporin 2 channels into the apical membrane, so more water is reabsorbed, and he says this raises blood volume and pressure.
Video by Armando Hasudungan on YouTube, embedded as published. The summary is written by PeptidesDNA from the video; every claim in it is the speaker’s. Not affiliated with or endorsed by the creator. Not medical advice.
