Effect of dexamethasone on gonadotrophin secretion in the gonadectomized sow and boar

Saline solution or dexamethasone (DXM, 35 micrograms/kg bodyweight) was injected intramuscularly twice daily for four days into five ovariectomized sows and five castrated boars. Blood samples from an indwelling jugular vein catheter were taken at 15 min intervals for 12 h prior to DXM injection and on the fourth day of treatment in order to compare the effect on variables describing the pulsatile secretion of luteinizing hormone (LH) and follicle stimulating hormone (FSH). Dexamethasone treatment caused a decrease (p less than 0.05) in the number of pulsatile episodes of LH secretion in both gonadectomized boars and sows resulting in a significant decrease in mean concentrations. Follicle stimulating hormone secretion parameters appeared to be unaffected by DXM injection in both groups of animals. It is concluded that previously described differences in LH suppression in boars and sows given glucocorticoids may be attributed to the influence of gonadal hormones.