Coexisting Prolactin-Secreting Macroadenoma, Hypopituitarism and Type 1 Diabetes Mellitus in a Young Adult Male Patient

The association between type 1 diabetes mellitus (DM) and pituitary prolactinoma is rarely reported in the literature. Herein we present a 23-year-old male patient with co-existing type 1 DM, pituitary macro-prolactinoma and panhypopituitarism secondary to mass effect. The patient presented with generalised symptoms including fatigability, cold hands, decreased insulin requirement secondary to frequent hypoglycaemic episodes two weeks following the diagnosis of type 1 DM. Initial blood workup showed evidence of possible secondary hypothyroidism. The full pituitary profile screen showed profound anterior hypopituitarism with a prolactin level of 67,168 miu/L (normal range 86-324 miu/L). Pituitary MRI showed macroadenoma, 37mm in size, with a suprasellar cystic extension but no chiasmal compression. It was treated medically with cabergoline and a repeat pituitary MRI after eight weeks of initiating treatment showed a 4-mm reduction in the size of the adenoma, and prolactin level decreased to 6,794 miu/L. The case was discussed at the Neurosurgical MDT and the outcome was to continue to monitor while on cabergoline. This case report is the second in the literature, which documented the association between type 1 DM and pituitary prolactinoma in adolescents. These patients might not present with the classical clinical features of hyperprolactinemia, and instead, they present with frequent hypoglycaemia and decreased insulin requirement due to secondary adrenal insufficiency as a consequence of the mass effect of the prolactinoma. Furthermore, non-specific symptoms, such as generalised tiredness and fatiguability, despite reasonable blood sugar control, in young patients with type 1 DM should trigger screening for all anterior pituitary hormones to exclude hypopituitarism.