Because male-typical behaviours developed as the result of a burst of testosterone, but in the absence of receptors for the hormone, the researchers suspect that the testosterone in the surge is being converted into oestrogen to carry out the newborn sexual-differentiation.
The hormone was prepared from human pituitary glands recovered from cadavers, and the absence of rigorous collection guidelines and purification procedures permitted contamination of the formulated drug with the agent that causes Creutzfeldt-Jacob disease, the human equivalent of "mad-cow disease, " or bovine spongiform encephalopathy (BSE).