Secretion of growth hormone and prolactin during progression of the luteal phase in healthy dogs: a review.
In some dogs the long exposure to high circulating progesterone levels during each oestrous cycle may result in a syndrome of growth hormone (GH) excess, i.e. acromegaly. The progesterone-induced GH production in dogs with acromegaly originates from the mammary gland. Also in healthy cyclic bitches, the pulsatile secretion pattern of GH changes during progression of the luteal phase, with basal GH secretion being higher and pulsatile GH secretion being lower when plasma progesterone concentration is high. This may be explained by partial suppression of pituitary GH release by progesterone-induced GH production in the mammary gland. Progesterone also modulates the secretion of prolactin in the bitch. In pregnant and overtly pseudopregnant bitches, the plasma prolactin concentration starts to rise about 1 month after ovulation, which is when the plasma progesterone concentration begins to decline. Also in healthy cyclic bitches, most prolactin is released during the second half of the luteal phase. The changes in GH and prolactin release during the luteal phase may promote the physiological proliferation and differentiation of mammary gland tissue in the bitch. In the early part of the luteal phase progesterone-induced mammary GH initiates proliferation of the mammary epithelium, whereas in the late luteal phase, when progesterone concentrations decrease, prolactin release increases and promotes lobuloalveolar differentiation.
Kooistra
H S
HS
Department of Clinical Sciences of Companion Animals and Faculty of Veterinary Medicine, Utrecht University, P.O. 80.154, NL-3508 TD Utrecht, The Netherlands. h.s.kooistra@vet.uu.nl
Okkens
A C
AC
D000818:Animals; D004285:Dogs / Q000502:physiology*; D030762:Estrous Cycle / Q000502:physiology*; D005260:Female; D013006:Growth Hormone / Q000378:metabolism*; D006801:Humans; D008183:Luteal Phase / Q000502:physiology; D011247:Pregnancy; D011388:Prolactin / Q000378:metabolism*
D011388:Prolactin; D013006:Growth Hormone