monal
gonadotrophs that store both gonadotrophins exist
together. Whereas in the pars distalis all three types of
gonadotrophs have been identified, few if any FSH monohormonal
cells exist in the pars tuberalis of the equine
pituitary. This heterogeneity in the pattern of LH and FSH
storage within the gonadotroph population is considered
the morphological basis for the differential regulation of
LH and FSH secretion throughout the equine reproductive
cycle (Tortonese et al., 2001).
The divergent pattern of LH and FSH release is more
pronounced in the mare than in many other domesticated
animal species (Fig. 1a and b). An early periovulatory rise
in peripheral concentrations of LH is accompanied by a
modest increase in FSH subsequently declining to its nadir