According to current concept,
macroprolactin is biologically inactive and, therefore, its accumulation in serum has little, if any, pathological significance. Authors present the history of a 80-year-old man who proved to have, among other associated disorders, an intra- and parasellar
pituitary tumor measuring 21x12x12 mm in size which was revealed by pituitary MRI. His hormonal evaluation indicated a marked
hyperprolactinemia mainly due to macroprolactinemia (total
prolactin, 514 ng/ml; reference range, 1.6-10.7 ng/ml;
macroprolactin 436 ng/ml, monomer
prolactin 78.2 ng/ml). Tests for function of the pituitary-thyroid axis showed a mild subclinical
primary hypothyroidism. The function of the pituitary-adrenal axis was normal, and other hormonal tests revealed low-normal serum
gonadotropins and decreased
testosterone level, whereas serum
insulin-like growth factor I was normal. Although the majority of current guidelines state that
dopamine-agonist treatment which is successfully used in
prolactin-producing
pituitary tumors and in other hyperprolactinemic disorders is unnecessary in patients with macroprolactinemia, the authors introduced a
dopamine-agonist,
quinagolide. During prolonged treatment, plasma
prolactin returned close to the upper limit of normal (12.3 ng/ml) and 9 months after the beginning of treatment pituitary MRI showed a remarkable shrinkage of the
pituitary tumor. Authors propose that in this patient the
pituitary tumor secreted
macroprolactin, and they recommend a treatment trial with
dopamine-agonist in pituitary macroadenomas associated with macroprolactinemia.