Dosing reproductive hormones is important for monitoring the oestrus, confirming reproductive disorders, gestation and others.

Luteinizing hormone (LH) may be dosed aiming the establishment of the Day zero of the oestral cycle of the bitch, once ovulation may occur within 48 hours following the oestrus. LH is produced by the adenohypophysis and stimulates the ovary. The main function of LH is to promote ovulation and the beginning of formation of the corpus luteum.

Estrogen is produced and released by the developing ovarian follicles. It reaches the maximum peak during the proestrus of the oestral cycle, which may range from the basal levels (5-15 pg/mL) up to 70 pg/mL in the late phase of proestrus. Other indication for estrogen dosing is the clinical suspicion of ovarian tumors and in lower rates, of adrenal tumors, as a small proportion of this hormone is produced by the adrenal glands. The main function of estrogen is the development of sexual characteristics of females, behavioral changes during the follicular phase of oestrus, stimulation of the endometrium and the mammary gland.

Progesterone is produced by the cells that underwent luteinization following serum LH raise, in the ovarian follicle. The peak of progesterone occurs following complete formation of corpus luteum. Progesterone is responsible for the maintenance of a favorable uterine environment for gestation. This hormone is a good marker of ovulation in bitches. The basal levels of progesterone during anestrus is 0,5-1,0 ng/ml. It may reach 3 ng/mL in the preovulatory period and may range from 5 to 18 ng/mL following ovulation. In the late phase of diestrus, it may reach up to 90 ng/mL. Relaxin, which is produced by the placenta, is exclusively detectable in pregnant animals. The raise in the levels of relaxin occurs between the 20th and the 30th days of gestation and its maximum peak occurs near the 45th day of pregnancy.

Testosterone is responsible for the development of the sexual characteristics of the males. The synthesis of testosterone occurs in the Leydig cells and in the interstitial cells of the testis. The main indications for dosing testosterone are for the hormonal assessment of cryptorchidism, clinical suspicion of intersex and infertility in males. The association of reproductive hormonal dosing with other endocrine tests are important for the diagnosis of endocrine-related skin disorders, ovarian remnant syndrome, infertility and others.

References

1.  González FHD. Introdução a endocrinologia veterinária. Acesso em 20 de jan de 2003. Disponível em: http://www6.ufrgs.br/bioquimica/. 2002.