High Seminal Fluid Calcium Is Associated With Higher Sperm Concentration in Infertile Men and Men From the General Population.

BACKGROUND

The extracellular calcium concentration is important for sperm function, maturation, and survival, however, studies exploring the link between seminal calcium and reproductive function have reported inconsistent findings.

OBJECTIVES

To investigate the association between seminal calcium levels and semen quality in both healthy and infertile men.

MATERIALS AND

METHODS

A total of 301 young men from the general Danish population who participated in a study of semen quality, and 228 infertile men who were supplemented with calcium (500 mg) + cholecalciferol (300,000 IU bolus followed by 1400 IU daily), or placebo in a randomized controlled trial were included. Each man underwent a physical examination, routine semen analysis, analysis of calcium concentrations in the seminal fluid, and blood sampling for assessment of PTH, testosterone, estradiol, inhibin B, and AMH.

RESULTS

In young men from the general population, sperm concentration was higher in those within the highest seminal calcium quartile (Q4: 9.0-19.2 mmol/L) compared with the lowest (Q1: 1.3-4.7 mmol/L; 53.0 million/mL vs. 31.0 million/mL, p = 0.010). Accordingly, infertile men in Q1 had the lowest sperm concentration (e.g., 6.6 vs. 22.5 million/mL in Q3), but also fewer progressively motile spermatozoa (p = 0.030). Supplementation with calcium and cholecalciferol did not affect seminal calcium concentration (p = 0.33), however, infertile men who experienced an increase in their seminal calcium concentrations > 30% at the end of intervention had a higher sperm concentration (p = 0.048) and total sperm count (p < 0.001) compared with baseline. There was a weak positive correlation between longitudinal changes of seminal calcium and serum estradiol (r = 0.17, p = 0.016).

CONCLUSIONS

Lower seminal calcium concentration is associated with poorer semen quality but was not influenced by calcium supplementation. Future research should focus on uncovering possible regulators, for instance, estrogens.

TRIAL REGISTRATION: ClinicalTrials.gov no. NCT01304927 (registered February 28, 2011).