Читать книгу Assisted Reproduction Techniques - Группа авторов - Страница 130

Human prolactin (PRL) is a polypeptide hormone comprising 199 amino acid residues. PRL is predominantly synthesized in and secreted from the lactotroph cells of the anterior pituitary gland under the control of dopamine. 80–90% of serum PRL circulates as the biologically active monomeric PRL, with dimeric and polymeric isoforms, termed macroprolactin, making up the remainder [1,2]. Macroprolactin has decreased biological activity and clearance. The most obvious function of PRL in humans is to support postpartum lactation [2]. During pregnancy, PRL concentration increases up to 10‐fold, and remains elevated during lactation under the stimulus of suckling [3]. PRL blocks the action of LH on the ovary or testis, producing hypogonadism [2]. Hyperprolactinemia inhibits ovulation, resulting in infertility. For this reason, measurement of serum PRL concentration is necessary when investigating ovulatory infertility [4]. Hyperprolactinemia may be asymptomatic, but in women of childbearing age it commonly presents with oligomenorrhea, loss of libido or galactorrhea [5].

Transient rises in PRL levels can occur during the late follicular phases of both natural and stimulated cycles [6]. There is evidence that high responders to ovarian stimulation are more likely to have higher incidence of transient hyperprolactinemia than intermediate or low responders [7]. Furthermore, serum PRL levels during an ART cycle are strongly correlated with peak estradiol levels [7]. However, there is no evidence that oocytes retrieved or fertilized, or the pregnancy rates are affected by transient hyperprolactinemia [6–9]. Such transient hyperprolactinemia during an ART cycle is therefore unlikely to be clinically significant.