Sex differences in histomorphology of the human carotid body

Knowledge of sex differences in the histomorphology of the human carotid body (HCB) is important in explaining the differences in respiratory function, responses and disease predisposition.1,2 Functionally, there are sex differences in the ventilatory response to hypoxia (VRH) and hypercapnia,1,3‒5 response in ventilatory control under acute or chronic hypoxic stimulation;6 morphine induced ventilatory depression,7 ventilatory roll off and post hypoxia facilitation8 and carotid body based control of ventilation.9 Further, ovarian hormones affect CB function.10 Regarding disease predisposition, hypoxia–mediated ventilatory diseases like sudden infant death syndrome, mountain sickness, high attitude pulmonary edema and sleep apnoea occur more commonly in males and postmenopausal females.10‒12 There are also sex differences in symptoms, diagnosis and consequences of obstructive sleep apnoea.13 There are, however, few studies on gender comparison of CB, with some denying variability.14