Hormonal control of prothrombin synthesis in rat liver microsomes, with special reference to the role of estradiol, testosterone and prolactin

Testosterone therapy increases the anticoagulant potential in men with opioid-induced hypogonadism: a randomized, placebo-controlled study

INTRODUCTION

Hypogonadism is prevalent during opioid treatment, and low testosterone concentrations are associated with cardiovascular disease. The effect of testosterone replacement therapy (TRT) on the coagulation system in men with hypogonadism is not clarified. We investigate the effects of TRT on the tissue factor (TF) and contact activation pathways of coagulation in opioid-treated men.

MATERIALS AND METHODS

This was a double-blinded, placebo-controlled study in 37 men with total testosterone < 12 nmol/L randomized to 24 weeks of testosterone injections (n = 17) or placebo (n = 20). Variables of the coagulation system were analysed at baseline and after 24 weeks. Measurements included the TF pathway (endogenous thrombin potential (ETP) and peak thrombin), the contact activation pathway (endogenous kallikrein potential (EKP) and peak kallikrein), coagulation factors (FVII, FX, prothrombin, and FXII), and inhibitors (tissue factor pathway inhibitor (TFPI), protein C, protein S, antithrombin, and C1 esterase inhibitor (C1inh)). Between-group differences at 24 weeks were determined with analysis of covariance. Within-group changes in TRT and placebo were analysed with paired t-test.

RESULTS

Between-group differences at 24 weeks were observed for ETP (P = 0.036), FVII (P = 0.044), FX (P = 0.015), prothrombin (P = 0.003), protein C (P = 0.004), and protein S (P = 0.038). Within the TRT group, ETP, peak thrombin, FVII, FX, prothrombin, TFPI, protein C, FXII, and C1inh decreased and protein S increased (all P < 0.05). Within the placebo group, coagulation outcomes were unchanged.

CONCLUSION

TRT affects the coagulation system in an anticoagulant direction through suppressed TF pathway in men with opioid-induced hypogonadism.

Levels of prolactin in relation to coagulation factors and risk of venous thrombosis

The pituitary hormone prolactin is thought to influence coagulation. We aimed to study the relation between prolactin levels, coagulation factors and risk of venous thrombosis (VT). We used data from a large population based case-control study into aetiology of first VT (MEGA-study). Prolactin levels were determined in 2,068 patients with VT and 2,785 age- and sex matched control subjects. The relation between levels of coagulation factors and prolactin was studied among the controls. In addition, odds ratios (OR) and 95% confidence intervals (95%CI) were calculated for the risk of VT for different cut-off points of prolactin levels based on percentiles determined in the controls. Restricted analysis was performed among cases in whom blood was sampled within six months after VT. We found a rise in factor VIII and von Willebrand factor with increasing levels of prolactin in the controls. An increased risk of VT was observed when blood was sampled within six months after thrombosis (OR 2.9, 95%CI 1.1–8.1) for prolactin levels above the 99th percentile (42.6 μg/l) relative to levels between the 20th to 80th percentile. When blood was sampled more than six months after VT no clear association could be observed (OR 1.3, 95%CI 0.7–2.3). In conclusion, we found a modest association between pro-lactin and symptomatic venous thromboembolism, particularly when blood was sampled close to the event. This may be explained by a causal relation or by prolactin being a marker of stress due to the thrombotic event.

Microcirculation and atherothrombotic parameters in prolactinoma patients: a pilot study

Atherothrombosis is a multifactorial process, governed by an interaction between the vessel wall, hemodynamic factors and systemic atherothrombotic risk factors. Recent in vitro, human ex vivo and animal studies have implicated the hormone prolactin as an atherothrombotic mediator. To address this issue, we evaluated the anatomy and function of various microvascular beds as well as plasma atherothrombosis markers in patients with elevated prolactin levels. In this pilot study, involving 10 prolactinoma patients and 10 control subjects, sidestream dark field (SDF) imaging revealed a marked perturbation of the sublingual microcirculation in prolactinoma patients compared to control subjects, as attested to by significant changes in microvascular flow index (2.74 ± 0.12 vs. 2.91 ± 0.05, respectively; P = 0.0006), in heterogeneity index (0.28 [IQR 0.18-0.31] vs. 0.09 [IQR 0.08-0.17], respectively; P = 0.002) and lower proportion of perfused vessels (90 ± 4.0% vs. 95 ± 3.0%, respectively; P = 0.016). In the retina, fluorescein angiography (FAG) confirmed these data, since prolactinoma patients more often have dilatated perifoveal capillaries. In plasma, prolactinoma patients displayed several pro-atherogenic disturbances, including a higher endogenous thrombin potential and prothrombin levels as well as decreased HDL-cholesterol levels. Prolactinoma patients are characterized by microvascular dysfunction as well as plasma markers indicating a pro-atherothrombotic state. Further studies are required to assess if prolactin is causally involved in atherothrombotic disease.

Is prolactin involved in the evolution of atherothrombotic disease?

Cardiovascular diseases (CVDs) account for approximately 30% of all deaths globally. The most important cause of CVD is atherothrombosis, in other words, narrowing of the arteries as a result of the deposition of cholesterol and other lipoid substances within the arterial wall. Several endocrine disorders have been linked to this pathological state. Recent clinical and experimental studies have suggested that prolactin, a pleiotropic pituitary hormone, may potentially contribute to CVD, either through direct modulation of local cellular processes within atherosclerotic plaques/thrombi and/or through influencing conventional cardiovascular metabolic risk factors. However, the precise role of prolactin in the pathology of CVD remains largely unknown. Here, the authors speculate whether prolactin-lowering treatment may become a future therapeutic approach in patients with elevated prolactin levels and concomitantly presenting with coexisting vascular disease or a significantly elevated risk for premature atherothrombotic vascular disease. Awareness of these new developments may also change our clinical opinions about therapeutic strategies in patients with prolactinomas.

Measurements of rat plasma coagulation proteins during prolonged exposure to diethylstilbesterol

The effects of diethylstilbesterol (DES) on concentration of selected plasma coagulation proteins in male rats was studied sequentially over a 28-day period. At the outset of the study, male rats underwent orchiectomy and implantation of a pellet containing DES 5.0 mg or a placebo pellet. At intervals of 7 days, 3 of the animals from each treatment group were sacrificed and blood samples were withdrawn for assay. Plasma concentrations of Factor II (prothrombin) and Factor VII, two vitamin K-dependent coagulation proteins, were significantly decreased in DES-treated animals (approximately 70% normal activity for both Factors) compared to placebo-treated animals. In contrast, Factor VIII activity was higher with DES treatment than with placebo. Plasma concentrations of both antithrombin III (AT III) and plasminogen were decreased in DES-treated animals compared to placebo by immunologic as well as activity assays. Albumin concentrations were not different between the two groups at any point of study, although both were increased at day 21 compared to beginning values. Fibronectin concentrations were slightly decreased in DES-treated animals compared to those which received placebo. The combination of orchiectomy and treatment with DES had profound metabolic effects on the animals; the DES treated animals had a mean body weight loss of 100 g after 28 days, while the placebo group gained an average of 78 g compared to a control group (no surgery) which had average weight gain of 85 g during the 28 day period of study.