Endocrine Abstracts

Introduction: Hyperprolactinemia is associated with suppression of the hypothalamic-pituitary-gonadal axis and it’s a frequent cause of infertility, occurring in about 30–40% of infertile women. The bioactive fraction of prolactin is a 23-kDa monomer. However, there are other isoforms with reduced or absent bioactivity, such as macroprolactin, which can be detected by the precipitation reaction by polyethylene glycol. Macroprolactinemia should be suspected in the presence of asymptomatic hyperprolactinemia.

Clinical case: 33-year-old woman referred to the Endocrinology appointment in April 2014 for hyperprolactinemia detected during the study of primary infertility with 7 years of evolution. Past medical history irrelevant. The age at menarche was 13, she had regular menstrual cycles, 0G 0P. She had been treated with bromocriptine from June 2011 to June 2013. Since then she took no pills. She had no galactorrhea or hirsutism. Biochemical study during follicular phase: normal renal and liver function, TSH 2.27 mIU/l (0.27–4.20), free T4 20.9 pmol/l (11.7–21.7), FSH 7.7 mUI/ml, LH 5.42 mUI/ml, estradiol 65.6 pg/ml, prolactin 1630 mU/l (127–637), total testosterone 0.17 ng/ml (0.06–0.82), delta 4-androstenedione 2.52 ng/ml (0.30–3.30), cortisol 606.2 nmol/l (171–536), ACTH 18.8, IGF-I 197 (109–324), 17-hydroxyprogesterone 0.7 ng/ml. Progesterone in luteal phase was 16.9 ng/ml (1.7–27.0). Prolactin levels remained high in subsequent measurements (1391, 1158 and 1133 mU/l). Pituitary MRI in 6/2013 and in 10/2014 were normal. Since she had asymptomatic hyperprolactinemia and normal pituitary MRI, we searched for macroprolactin that was positive (percentage of prolactin recovery - polyethylene glycol precipitation: 8%).

Discussion: This case reveals the difficulty of etiological diagnosis of hyperprolactinemia in a woman with a history of primary infertility. However, asymptomatic and slightly elevated levels of prolactin associated with normal pituitary MRI has raised the hypothesis of macroprolactinemia. The diagnosis of this entity was very important to avoid further inappropriate treatment with dopaminergic agonists and to refer the couple to medically assisted reproduction treatment.