Difficulties in diagnosis of adenomas with mixed prolactin and growth hormone secretion: Case presentation

Hyperpolactinemia is a persistent excess of prolactin in the blood serum. The symptom complex of hyperprolactinemia primarily consists of disturbances in function of the reproductive system. The secretion of prolactin is under complex neuroendocrine control, which involves factors of different nature: neurotransmitters, hormones of the peripheral endocrine glands. In most cases, prolactin is secreted by pituitary cells - lactotrophs, but in some cases, hypersecretion of prolactin is combined with an excess production of growth hormone, which is typical for tumors originating from the line of progenitor cells of lactotrophs and somatotrophs of the pituitary gland, mammosomatotrophs. In this case, symptoms of hyperprolactinemia are accompanied by clinical manifestations of acromegaly. In patients with acromegaly, the cause of hyperprolactinemia may be pituitary stalk compression or mixed secretion of prolactin and growth hormone. Differentiation of lactotropic and somatotropic pituitary cells is determined by transcription factor Pit-1. These cell lineages are closely connected, and this may be one of the reasons for formation of tumors with mixed secretion. Reports of late presentation of acromegaly in patients previously diagnosed with prolactinomas have also been described in literature. Clinical manifestations of hyperprolactinemia can cause the patient to seek doctor’s attention before acromegalic changes in appearance develop. Careful attention is needed both to the primary diagnosis and to the clinical course of the disease in patients with hyperprolactinemia and pituitary adenoma: full assessment of hormonal status with mandatory evaluation of IGF-1 is crucial at initial examination, during further observation it may be advised to consider periodic evaluation of IGF-1 in addition to assessment of prolactin and the size of adenoma. Pituitary adenomas with mixed secretion may have a poorer prognosis.