Clinical Adverse Effects of Prolactin

Halbreich and Kahn [3] proposed that many of the clinical adverse consequences of HPRL could be accounted for by its effects on the HPG axis. HPRL is associated with suppression of gonadotropin pulsatile release, which in turn inhibits the release of luteinizing hormone (LH) and follicle-stimulating hormone (FSH) from the pituitary leading to suppression of ovarian and testicular function in turn leading to hypogonadism [3, 27]. This potentially further led to a range of menstrual disorders, reduced fertility in both sexes, decreased sexual function in men and women including decreased libido, increased risk of cardiovascular disorders, galactorrhoea, anxiety and depression. Halbreich and Kahn [3] also postulated that adverse events such as an increased risk of breast cancer were possibly associated with HPRL. This hypothesis is supported by Harvey et al. [6] who identified that PRL has a direct action on breast tissue where it can act as a mitogen in the mammary gland. Furthermore, PRL stimulates the growth and motility of human breast cancer and acts as a potent survival factor protecting human breast cancer cells from apoptosis.

The last decade has seen a new research focus on the secondary impact of antip-sychotics on gonadal hormones and hypogonadism through HPRL in schizophrenia. Smith et al. [22] reported the impact of typical antipsychotics, with a 2-year minimum exposure on patients with schizophrenia, finding that 75% of the females and 34% of the males have HPRL. The rates of hypogonadism were 85% and 6.4% in females and males, respectively. This highlights that PRL levels are a relatively good indicator of risk of hypogonadism, but in females suggests that HPRL levels at the top end of the normal range may also indicate hypogonadism. Howes et al. [28] investigated 103 patients with schizophrenia or schizoaffective disorder with a medium treatment duration of 3.3 years with antipsychotics. The rates of hypogonadism in females was 79%, and 92% of the women had hypo-oestrogenism and 28% of the men showed hypotestosteronism.

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