Ghrelin's role in reproduction was first suggested by its wide
expression in many human reproductive tissues including its
immunohistochemical expression in the human ovary. Ghrelin
expression is identified in the seminiferous tubuli of the interstitial
Leyding and Sertoli cells in male testicles, whereas it is identified in the
ovarian hilus interstitial cells and mature corpus lutea in females.
It is postulated that ghrelin plays a local regulatory role in the male
and female gonads. In females, Ghrelin acts centrally by suppressing
hypothalamic GnRH release and GnRH-induced gonadotropin secretion
by the pituitary; and in gonads it acts by increasing luteolytic factors
such as PGF2 alfa, and ghrelin inhibiting estradiol and progesterone
biosynthesis in granulose-lutein cells as well as granulosa cell (GC)
proliferation.
This potential regulatory effect on steroidogenesis and ovarian
cellular function led to the hypothesis that ghrelin may mediate the
relationship between metabolism and oocyte quality in addition to possible role in the regulation of embryo development in as the cleavage
development before the six-cell stage of a preimplantation human
embryo depends solely on maternally inherited material.
Ghrelin levels can, therefore, be an indicator of an underlying
pathology as in humans in states of chronic malnutrition such as
anorexia nervosa, serum ghrelin levels may be increased, while in other
conditions it could be associated with decreased ghrelin levels such as
obesity and polycystic ovarian syndrome (PCOS).