The passage addresses that NPY in conjunction with GnRH (but not by itself) can cause increased secretion of LH vs GnRH alone. Scientists are hopeful that NPY can be used in combination with GnRH to treat certain cases of female infertility. Individuals with a deficiency in what receptor system would be most likely to benefit from such a treatment?

A. GnRH
B. LH
C. NPY
D. LH and NPY

The individuals with a deficiency in GnRH would be the most likely to get benefit from the treatment as NPY elevates the usual activity of GnRH in instigating the LH levels in the blood. Option B is incorrect, as NPY stimulates LH that then combines with the receptors, which are deficient. To some degree, the excess LH would have helped, however, not as much as if GnRH receptors are lacking.

Only if there is a deficiency of GnRH receptors, then the NPY would have helped the most as NPY would utilize a distinct receptor, and thus, normal levels of LH would get generated.