Sexual Dimorphism and Aging Effects on Pituitary Gonadotroph Structure and Secretion in Dromedary Camels: Immunohistochemical and Ultrastructural Insights

This study investigated age- and sex-related variations in pituitary gonadotroph morphometry and serum luteinizing hormone (LH) and follicle-stimulating hormone (FSH) concentrations in 90 clinically healthy dromedary camels (Camelus dromedarius). Animals were grouped into three age categories (2–4, 5–10, and ≥11 years), with equal representation of males and females. The precise reproductive status of the female camels (e.g., estrous stage or pregnancy status) was not determined and should be considered when interpreting the endocrine findings. Immunocytochemical analysis revealed significant age- and sex-related differences in gonadotroph number and morphometric characteristics (p < 0.05). Gonadotroph counts were 8.3 ± 0.4, 9.4 ± 0.5, and 8.1 ± 0.4 cells in the 2–4, 5–10, and ≥11-year age groups, respectively, with males showing a higher overall count than females (9.1 ± 0.4 vs. 8.2 ± 0.3; p < 0.05). Overall cell size, cell area, cell volume, nucleus area, and nucleus volume were also greater in males than females (p < 0.05). The largest nucleus size, nucleus area, and nucleus volume were observed in camels ≥11 years of age, with values of 4.7 ± 0.1 µm, 18.5 ± 0.8 µm2, and 60.3 ± 4.1 µm3, respectively. Ultrastructural analysis further showed a significant sex difference in granule size (58.0 ± 0.7 vs. 52.2 ± 0.8 nm) and granule percentage (56.2 ± 3.6 vs. 43.5 ± 3.3% in males and females, respectively; p < 0.05). Serum FSH concentrations were higher in males than females (4.8 ± 0.1 vs. 4.2 ± 0.1 µIU/mL; p < 0.05), whereas LH concentrations were 1.2 ± 0.1 and 1.2 ± 0.1 µIU/mL in males and females, respectively. LH concentration was highest in 5–10-year-old males (1.3 ± 0.2 µIU/mL), while FSH concentration was highest in ≥11-year-old males (4.8 ± 0.2 µIU/mL). Pearson correlation analysis demonstrated significant positive associations between gonadotroph morphometric parameters and circulating gonadotropins, with correlations ranging from 0.52 to 0.74 for cell/nuclear measurements with LH and FSH. Overall, the findings demonstrate marked age- and sex-associated differences in gonadotroph morphology, ultrastructure, and circulating gonadotropin concentrations in dromedary camels, with males generally exhibiting greater gonadotroph dimensions and secretory granule characteristics. These structural and endocrine differences provide evidence of age- and sex-related variation in pituitary gonadotrophic activity, although the findings should be interpreted in light of the cross-sectional design and the undetermined reproductive status of female camels. Overall, these findings demonstrate pronounced age- and sex-associated differences in pituitary gonadotroph morphology, ultrastructure, and endocrine activity, with males generally exhibiting greater cellular and secretory characteristics. The findings provide novel morphological and endocrine evidence of reproductive aging and sexual dimorphism in the dromedary camel pituitary and may contribute to improved understanding of reproductive function across different life stages. However, interpretation should consider the cross-sectional design and the inability to determine the precise reproductive stage of female camels before slaughter.