The present intervention generally relates to compositions comprising a PDE11 inhibitor for increasing cortisol levels in a subject, or for increasing the production of cortisol from adenocortical cells in a subject. Aspects of the invention relate to the use of a PDE11 inhibitor in a method of treatment of low cortisol levels and/or adrenal insufficiency in a subject, or a method of treating a disease or disorders associated with adrenal insufficiency. Aspects of the invention relate to PDE11 inhibitors belonging to compounds of formula (I)-(VI), and their use alone or in combination with long-term corticosteroid treatment to elevate cortisol levels in a subject, and/or to treat adrenal insufficiency. Another aspect relates to kits comprising PDE11 inhibitors for administration to a subject, pharmaceutical compositions comprising compounds of formula (I)-(VI) for use in methods to increase cortisol levels and/or treat adrenal insufficiency, and their use as an adjuvant for treatment of cancer or other disorders such as psychiatric diseases where elevating cortisol levels would be beneficial to the subject.