An inhibition of sex hormone secretion is observed in domestic animals exposed to cadmium in experimental conditions. Ninety-six gilts (Duroc × Landrace × Yorkshire, initial weight 27.59 kg) were randomly assigned into four different groups with three replications in each group (eight gilts per replication). The groups received the corn–soybean basal diet and supplemented with 0, 0.5, 5.0 and 10.0 mg/kg cadmium (as CdCl2) respectively. The feeding trial was ended when body weight of pigs was approximately 90 kg. The results showed that 10.0 mg/kg cadmium significantly decreased average daily gain (p < 0.05) and increased feed/gain ratio (p < 0.05) of pigs. Follicle-stimulating hormone, luteinizing hormone, oestradiol (E2) and progesterone levels in serum of the pigs fed the diet supplemented with 10.0 mg/kg cadmium were lower significantly than those of the control (p < 0.05). Compared with the control, no changes were found in the levels mentioned above when the pigs fed the diet supplemented with 0.5 or 5.0 mg/kg cadmium (p > 0.05). The changes of regulatory mechanism of the pituitary–ovary axis may be the result of cadmium accumulation in pituitary and ovary and should be investigated further.