Gestational diabetes insipidus only happens during pregnancy, while primary polydipsia develops with large volumes of urine.
Primary polydipsia or dipsogenic diabetes insipidus or psychogenic polydipsia happens by the excretion of large volumes of diluted urine. ADH production or damage is not the problem, but the intake of excessive fluids is the issue.
If you drink excessive amounts of fluids for a prolonged amount of time, these fluids can cause damage to the kidneys and suppress ADH. This makes your body unable to concentrate the urine. Primary polydipsia may be the cause of abnormal thirst brought on by damage to your thirst-regulating mechanism located in the hypothalamus. Primary polydipsia can also be a cause of mental illness.