In ovariectomized ewes, intravenous administration of 400 ng/kg endotoxin suppresses gonadotropin-releasing hormone (GnRH) pulsatile release into hypophyseal portal blood, reduces mean GnRH collection rate by 63% and pulse amplitude by 68% within 7 hours, and simultaneously suppresses luteinizing hormone (LH) concentrations, pulse amplitude, and pulse frequency, indicating central inhibition of the reproductive neuroendocrine axis.

A bacterial toxin in the blood triggers the brain's immune response, which directly slows down the brain's reproductive signal generator. This causes the signal pulses to become weaker and less frequent, which in turn tells the pituitary gland to release less of the hormone that controls ovulation. At the same time, the brain's stress system turns on, releasing hormones and raising body temperature, which further dampens the reproductive signal.