Antidiuretic Hormone (ADH)

Structure and Synthesis

Structure: ADH is a peptide hormone consisting of nine amino acids.

Synthesis: It is produced by the hypothalamus and transported to the posterior pituitary gland for storage and release.

Mechanism of Action

Target Tissues: ADH acts primarily on the kidneys, but it also has effects on blood vessels.

Kidney Reabsorption: ADH increases the permeability of the collecting ducts in the kidneys, allowing for increased reabsorption of water back into the bloodstream.

Regulation

Osmoreceptors: ADH release is stimulated by the hypothalamic osmoreceptors in response to changes in blood osmolarity (concentration of solutes).

Baroreceptors: Low blood pressure can also stimulate ADH release to help maintain blood volume and pressure.

Functions and Effects

Water Conservation: ADH helps to conserve water by reducing urine volume and increasing its concentration.

Blood Pressure Regulation: By conserving water, ADH indirectly helps to maintain blood pressure by increasing blood volume.

Disorders

Diabetes Insipidus: This condition is characterized by a deficiency of ADH, leading to excessive urination and thirst.

Syndrome of Inappropriate ADH (SIADH): In this condition, excessive ADH secretion leads to water retention and dilutional hyponatremia.

Clinical Relevance

ADH Analogs: Synthetic analogs of ADH, such as desmopressin, are used in the treatment of diabetes insipidus and other related conditions.

Diagnosis: Measurement of ADH levels and response to water deprivation or hypertonic saline tests can help in diagnosing certain disorders related to ADH.

Conclusion

Antidiuretic hormone (ADH) plays a crucial role in maintaining water balance and blood pressure in the body. Its effects on kidney function and water reabsorption are vital for preventing dehydration and maintaining overall fluid homeostasis.