Background & Objectives: Blood leukocyte count and differential count varies from individual to individual and diurnal changes are noted in various studies. In present study we are investigating the effect of cyclic changes in gonadotropic hormones during normal menstrual cycle on the differential leukocyte count and in particular the nuclear lobe variation in the different phases of menstrual cycle in young women of 18-22 years old with normal past menstrual cycles.

Methodology: First year undergraduate students of Pushpagiri Medical College in the age group of 18-22 years were included in the study. 44 healthy female students with regular menstrual cycle of 28±2days duration participated in the study, students   with   irregular cycles, gynaecological disorders; history of drug intake and acute illness were excluded from the study. The blood was collected under aseptic precautions and peripheral blood smears were formed. The smears were stained with Leishman’s stain following standard protocol and labelled them. The differential leukocyte count and arneth count were observed in the stained smear and recorded. To study variation the blood samples were collected on 5th day of the cycle (menstrual), 14^th day of the cycle (proliferative) and 21^st day of the cycle (luteal). The results were analysed using one way ANOVA between 3 groups and posthoc analysis if applicable.

Results & Conclusion: Different phases of menstrual cycle showed an statistically significant difference in Differential count of Neutrophils & Lymphocytes but other cells Eosinophil count, Monocyte & Basophil count had no significant difference which suggested that gonadotropic hormones had influence on leukocytes both granulocyte (Neutrophil) & agranulocyte (Lymphocyte) where we noticed increased Neutrophil count during luteal phase and least increase in number of Lymphocytes during luteal phase. In arneth count we had statistically significant difference in 2, 3, 4 and 5 lobed nuclei of Neutrophils and specifically 2 and 3 lobed Neutrophil count increased in luteal phase suggesting new (young) neutrophils released in the circulation 

Keywords: Arneth count, menstrual cycle, white blood corpuscle.