The role of prolactin in the menopause

Hyperprolactinemia in the postmenopause: versions and contraversions

The prevalence of hyperprolactinemia in postmenopausal women is unknown and has been estimated as infrequent by many studies. Prolactinomas found after menopause are usually macroadenomas and remain unrecognized for a long time due to atypical clinical signs or their absence. The growth potential of prolactinomas persists after menopause, most of them are invasive and accompanied by high prolactin levels. Treatment with dopamine agonists is usually long-term, the goals of which are to reduce tumor size, normalize prolactin levels and the negative effects of hyperprolactinemia. Treatment with cabergoline makes it possible to achieve remission of the disease in the first years after discontinuation, however, the proportion of relapses in postmenopausal women increases 5 years after discontinuation of the drug. Remission of prolactinomas is not evident in postmenopausal women. The modern management of patients with prolactinoma and/or hyperprolactinemia does not have clear positions in the postmenopausal period. Controversial issues remain: an ambiguous relationship between prolactin levels and breast cancer, there are no convincing conclusions on the improvement of bone mineral density and/or a decrease in the risk of fractures with normalization of prolactin levels, there are no data on metabolic parameters after the end of treatment with dopamine agonists, conflicting information about the relationship of prolactin levels and the severity of the manifold manifestations of the climacteric syndrome. The use of estrogen-progestin drugs in women with hyperprolactinemia/prolactinomas is also not well understood. Thus, the problem of hyperprolactinemia in the perimenopausal and postmenopausal period is underestimated and requires additional research, as well as the development of diagnostic and therapeutic strategies for potential benefits in terms of weight loss, improving insulin sensitivity, reducing the risk of fractures, maintaining sexuality and psycho-emotional well-being.

Age-Related Differences in Hearing Function and Cochlear Morphology between Male and Female Fischer 344 Rats

Fischer 344 (F344) rats represent a strain that is frequently used as a model for fast aging. In this study, we systematically compare the hearing function during aging in male and female F344 rats, by recording auditory brainstem responses (ABRs) and distortion product otoacoustic emissions (DPOAEs). In addition to this, the functional parameters are correlated with the cochlear histology. The parameters of the hearing function were not different in the young (3-month-old) male and female F344 rats; the gender differences occurred only in adult and aged animals. In 8–24-month-old males, the ABR thresholds were higher and the ABR amplitudes were smaller than those measured in females of the same age. There were no gender differences in the neural adaptation tested by recording ABRs, elicited by a series of clicks with varying inter-click interval (ICI). Amplitudes of DPOAEs in both the males and females decreased with age, but in the males, the decrease of DPOAE amplitudes was faster. In males older than 20 months, the DPOAEs were practically absent, whereas in 20–24-month-old females, the DPOAEs were still measurable. There were no gender differences in the number of surviving outer hair cells (OHC) and the number of inner hair cell ribbon synapses in aged animals. The main difference was found in the stria vascularis (SV). Whereas the SV was well preserved in females up to the age of 24 months, in most of the age-matched males the SV was evidently deteriorated. The results demonstrate more pronounced age-related changes in the cochlear morphology, hearing thresholds, ABR amplitudes and DPOAE amplitudes in F344 males compared with females.

Prolactin determinants in healthy women: A large cross-sectional study within the EPIC cohort

BACKGROUND

Experimental and epidemiologic data suggest that higher circulating prolactin is associated with breast cancer risk; however, how various risk factors for breast cancer influence prolactin levels in healthy women is not clear.

METHODS

We analyzed cross-sectional associations between several suggested reproductive and lifestyle risk factors for breast cancer and circulating prolactin among pre- and postmenopausal women, taking into account the use of current postmenopausal hormone therapy, among 2,560 controls from a breast cancer nested case-control study within the EPIC cohort.

RESULTS

Adjusted geometric mean prolactin levels were significantly higher among premenopausal women, and among postmenopausal women using hormone therapy compared with nonusers (8.2, 7.0, and 6.3 ng/mL, respectively; Pcat = <0.0001). Furthermore, prolactin levels were significantly higher among users of combined estrogen-progestin hormone therapy compared with users of estrogen-alone hormone therapy (6.66 vs. 5.90 ng/mL; Pcat = 0.001). Prolactin levels were lower among parous women compared with nulliparous women (8.61 vs. 10.95 ng/mL; Pcat = 0.0002, premenopausal women); the magnitude of this difference depended on the number of full-term pregnancies (22.1% lower, ≥3 vs. 1 pregnancy, Ptrend = 0.01). Results for parity were similar but lower in magnitude among postmenopausal women. Prolactin did not vary by other studied factors, with the exception of lower levels among postmenopausal smokers compared with never smokers.

CONCLUSIONS

Our study shows that current hormone therapy use, especially the use of combined hormone therapy, is associated with higher circulating prolactin levels in postmenopausal women, and confirms prior findings of lower circulating prolactin in parous women.

IMPACT

Our study extends the knowledge linking various breast cancer risk factors with circulating prolactin.

The association of breast mitogens with mammographic densities

Radiologically dense breast tissue (mammographic density) is strongly associated with risk of breast cancer, but the biological basis for this association is unknown. In this study we have examined the association of circulating levels of hormones and growth factors with mammographic density. A total of 382 subjects, 193 premenopausal and 189 postmenopausal, without previous breast cancer or current hormone use, were selected in each of five categories of breast density from mammography units. Risk factor information, anthropometric measures, and blood samples were obtained, and oestradiol, progesterone, sex hormone binding globulin, growth hormone, insulin-like growth factor-I and its principal binding protein, and prolactin measured. Mammograms were digitised and measured using a computer-assisted method. After adjustment for other risk factors, we found in premenopausal women that serum insulin-like growth factor-I levels, and in postmenopausal women, serum levels of prolactin, were both significantly and positively associated with per cent density. Total oestradiol and progesterone levels were unrelated to per cent density in both groups. In postmenopausal women, free oestradiol (negatively), and sex hormone binding globulin (positively), were significantly related to per cent density. These data show an association between blood levels of breast mitogens and mammographic density, and suggest a biological basis for the associated risk of breast cancer.

The effects of six months of treatment with a low-dose of conjugated oestrogens in menopausal women

OBJECTIVE

Hormone replacement therapy (HRT) is usually prescribed as medium- to high-dose formulations. Little is known, however, about dose-dependency of oestrogen effects on plasma hormone levels, markers of cardiovascular risk in lipid metabolism and the haemostatic system, or markers of bone turnover.

SUBJECTS AND DESIGN

In an open trial, three groups of 12 or 13 healthy, non-obese postmenopausal women received conjugated equine oestrogens (CEE) for 6 months at doses of 0.3 mg/day (group 1), 0.6 mg/day (group 2) or 1.25 mg/day (group 3). From day 1 to day 10, CEE was administered alone, and from day 11 to day 21, in combination with 5 mg of medrogestone. Each treatment cycle was followed by a pause of 7 days. Fasting blood samples were obtained before treatment as well as on days 10, 21 and 28 of the first, third and sixth months on treatment. All results obtained on day 10 were grouped together as phase A, on day 21 as phase B, and on day 28 as phase C.

MEASUREMENTS

Plasma concentrations of oestradiol (E), dehydroepiandrosterone sulphate (DHEA-S), total testosterone (T), FSH, PRL, sex hormone binding globulin (SHBG), type I procollagen propeptide (PICP) and the cross-linked carboxyterminal telopeptide of type I collagen (ICTP), total cholesterol, HDL-cholesterol, triglycerides (TG), apolipoprotein (apo) A-1, apo B, lipoprotein(a)[Lp (a)], fibrinogen, factor VIIc and plasminogen activator inhibitor 1 (PAI-1) were evaluated with commercially available kits.

RESULTS

Dose-dependently, the three regimens increased E, SHBG and factor VIIc activity and decreased FSH, DHEAS, cholesterol, LDL-cholesterol and apoB. HDL-cholesterol and apoA-1 were slightly decreased in group 1 but increased in groups 2 and 3. The high CEE dosage in group 3 resulted in a significant increase of TG and decrease of Lp(a) and PAI-1. Markers of bone turnover were not significantly changed by any CEE dosage.

CONCLUSIONS

Six months of treatment with 0.3 mg/day of conjugated equine oestrogen significantly lowers serum levels of total cholesterol and LDL-cholesterol without causing the adverse increases of triglycerides or factor VIIc, which were observed at higher doses. However, this low-dose treatment did not yield the maximal LDL-cholesterol lowering effect. Moreover, the positive effects of HRT on HDL-cholesterol, apolipoprotein A-I, lipoprotein (a) and plasminogen activator inhibitor-1 required at least the medium dose of 0.6 mg conjugated equine oestrogens per day. Therefore, further studies are needed to determine which dose of conjugated equine oestrogens has the optimal effect on cardiovascular risk and bone turnover.

Hormonal replacement therapy in menopausal women with a history of hyperprolactinemia

Hyperprolactinemia is involved in almost 30% of infertility problems. At the onset of menopause, prolactin levels often decrease; however, no data are available regarding the course of hyperprolactinemia after menopause with hormonal replacement therapy (HRT). A retrospective study was undertaken in our department to evaluate the potential role of estrogens in women with a history of hyperprolactinemia. Twenty-two patients, with hyperprolactinemia before menopause, were followed-up. Group I included 11 patients who withdrew bromocriptine treatment when menopause was confirmed. These patients were placed on HRT with no other medication administered. HRT was a combination of percutaneous estradiol gel and an oral progestin. Group II included 7 women treated by bromocriptine before menopause and after menopause concomitantly with HRT. Group III included 4 patients who did not receive HRT or other treatments once menopause was diagnosed. The mean serum prolactin level was unchanged in Group I (22.8+/-21.7 before and 22.8+/-16.1 ng/ml after HRT) while it increased but not significantly from 8.1+/-5.2 to 16.0+/-11.7 ng/ml in Group II. The mean duration of HRT was 42.8+/-23.8 (7-81) and 37.3+/-31.0 (6-99) months in Group I and II respectively. In Group III patients, PRL levels decreased spontaneously from 61.2+/-39.8 to 33.0+/-34.7 ng/ml. In conclusion, in this population of menopausal patients with a history of moderate hyperprolactinemia, HRT did not seem to affect plasma prolactin levels.