When is antidiuretic hormone secreted?

When osmolarity increases above the threshold, the ever-alert osmoreceptors recognize this a the cue to stimulate the neurons that secrete antidiuretic hormone.. Secretion of (MORE)
In Bladder

What hormone reduces urine output?

ADH (Antidiuretic hormone). ADH is secreted in the pituitary gland and it works by increasing the amount of water reabsorbed in the kidney and hence, less urine is produced.