Sexual function and depressive symptoms in men with hypoprolactinaemia secondary to overtreatment of prolactin excess: A pilot study

Neuropsychological complications of hypoprolactinemia

Prolactin (PRL) is primarily produced by the pituitary lactotrophic cells and while initially named for its role in lactation, PRL has several other biological roles including immunomodulation, osmotic balance, angiogenesis, calcium metabolism, and appetite regulation. Most of the PRL-related literature has traditionally focused on hyperprolactinemia, whereas hypoprolactinemia has received little attention. There is evidence to suggest that PRL receptors are widely distributed within the central nervous system including the limbic system. Furthermore, PRL has been shown to play key role in the stress regulation pathway. Recent data also suggest that hypoprolactinemia may be associated with increased sexual dysfunction, anxiety, and depression. In this paper we discuss the current understanding regarding the neuropsychological impact of hypoprolactinemia and highlight the need for adequately defining hypoprolactinemia as an entity and consideration for future replacement therapies.

Hypoprolactinemia. Does it matter? Redefining the hypopituitarism and return from a mumpsimus : "Absence of proof is not the proof of absence"

Prolactin (PRL) is secreted by the lactotroph cells in the anterior pituitary gland which is under inhibitory control of dopamine. The mature human PRL has more than 300 physiological actions including lactation, reproduction, homeostasis, neuroprotection, behavior, water and electrolyte balance, immunoregulation and embryonic and fetal development. PRL is involved in the growth and development of mammary gland, preparation of the breast for lactation in the postpartum period, synthesis of milk, and maintenance of milk secretion. Abnormalities in the synthesis and secretion of PRL may result in hyperprolactinemia or hypoprolactinemia. Although hyperprolactinemia has been extensively investigated in the literature, because of the subtle or unclearly defined symptoms, hypoprolactinemia is a less-known and neglected disorder. Failure of lactation is a well-known clinical manifestation of hypoprolactinemia. Recent studies reveal that hypoprolactinemia may have some effects beyond lactation such as increased risk for metabolic abnormalities including insulin resistance, abnormal lipid profile, obesity and sexual dysfunction. Very low level of PRL is suggested to be avoided in patients receiving dopamin agonist treatment to prevent unwanted effects of hypoprolactinemia. Another important point is that hypoprolactinemia is not included in the classification of hypopituitarism. Anterior pituitary failure is traditionally classified as isolated, partial and complete (panhypopituitarism) hypopituitarism regardless of prolactin level. Therefore, there are two kinds of panhypopituitarism: panhypopituitarism with normal or high PRL level and panhypopituitarism with low PRL level. In this review, we present two personal cases, discuss the diagnosis of hypoprolactinemia, hypoprolactinemia associated clinical picture and suggest to redefine the classification of hypopituitarism.

Cardiometabolic profile of young women with hypoprolactinemia

PURPOSE

Unlike hyperprolactinemia, clinical significance of prolactin deficiency remains poorly understood. The aim of this study was to assess the cardiometabolic profile of patients with low prolactin levels.

METHODS

The study population consisted of three groups of young women. Two groups were chronically treated with cabergoline but differed in prolactin levels, which were either abnormally low (group A; n = 16) or within the reference range (group B, n = 23). Group C, serving as a control group, included 28 drug-naïve women with normal prolactin levels. The dose of cabergoline in group A was then tapered down. Glucose homeostasis markers, plasma lipids and circulating levels of hormones, uric acid, high-sensitivity C-reactive protein (hsCRP), fibrinogen and homocysteine, as well as the carotid intima-media thickness were assessed at baseline and 6 months later.

RESULTS

Compared with subjects with normal prolactin levels, women with hypoprolactinemia had higher levels of 2-h postchallenge glucose, glycated hemoglobin, triglycerides, uric acid, hsCRP and fibrinogen, lower values of HDL-cholesterol, total testosterone and free androgen index, as well as reduced insulin sensitivity. No differences in these variables were observed between groups B and C. Apart from prolactin normalization, cabergoline dose reduction reversed all laboratory disturbances reported in group A.

CONCLUSION

The obtained results suggest that hypoprolactinemia in women of reproductive age may increase cardiometabolic risk.

Metabolic effects of prolactin and the role of dopamine agonists: A review

Prolactin is a polypeptide hormone that is well known for its role in reproductive physiology. Recent studies highlight its role in neurohormonal appetite regulation and metabolism. Elevated prolactin levels are widely associated with worsening metabolic disease, but it appears that low prolactin levels could also be metabolically unfavorable. This review discusses the pathophysiology of prolactin related metabolic changes, and the less commonly recognized effects of prolactin on adipose tissue, pancreas, liver, and small bowel. Furthermore, the effect of dopamine agonists on the metabolic profiles of patients with hyperprolactinemia are discussed as well.