*1.1.3. Disorders of sexual development*

estruses. Normally, bitches experience estrus at 4–10 month (mean 6–7 months) intervals. Cycles shorter than 4 months or longer than 10 months are abnormal and can cause infertility

Factors that lead to primary anestrus include ovariectomy or ovariohysterectomy at early age, silent heat (subestrus), abnormalities in sexual differentiation (chromosomal and genetic disorders), use of progesterone or glucocorticoids, congenital hypothyroidism, certain systemic diseases, ovarian anomalies or ovarian aplasia, progesterone-releasing ovarian cysts,

Secondary anestrus may result from dysfunction of the thyroid gland or adrenal cortex, as well as nonendocrinological disorders, cachexia, obesity, and use of cycle-inhibiting drugs. Silent heat, luteal cysts, and some ovarian tumors may also lead to secondary anestrus as well as to

If taken from another person, the bitch may have been sterilized, which a new owner may overlook. Presence of a tattoo in the inguinal region and palpation or inspection of a scar from operation in the ventral wall of the abdomen may be indicators of ovariohysterectomy. However, it should be kept in mind that such a scar may be present if any intra-abdominal operation has been performed, so it may be premature to conclude that the scar resulted from ovariohysterectomy. Serum LH level measurement may be used to identify bitches that have undergone ovariohysterectomy, as serum LH is continuously high in such bitches as a result of the absence of negative feedback on LH (because the ovaries have been removed). Although elevation in serum LH provides information about ovariohysterectomy, note that this indicator may also be seen in ovarian dysfunction or during the preovulatory period (i.e., the preovulatory LH peak). Therefore, repeated measurements are required to confirm and experimental laparotomy may also be performed for a definitive diagnosis [8]. Whether ovariohysterectomy has been performed may also be detected by measuring the serum estrogen level before and 60–90 min after intravenous administration of 0.02–0.03 μg/kg buserelin. If ovariohysterecto-

Anti-müllerian hormone (AMH) measurement may also show whether a bitch has undergone ovariohysterectomy. AMH levels are found to be significantly lower in bitches that have

Silent heat is defined as the maintenance of ovarian functions without the presence of vulvar edema, serosanguinous vaginal discharge, and charm for male dogs. Silent heat may be observed for several cycles before first estrus in younger bitches of smaller breeds. These animals may be evaluated as "anestrus" because the pet owner may not find the external signs of estrus, or they may be identified as healthy male dogs although ovarian functions continue

my has been performed, estrogen levels will be found above 15–20 pg/mL.

undergone ovariohysterectomy compared to nonsterilized bitches [9, 10].

[2–6].

and autoimmune oophoritis [2, 7].

128 Canine Medicine - Recent Topics and Advanced Research

*1.1.1. History of ovariohysterectomy*

primary anestrus [4, 5].

*1.1.2. Silent heat (subestrus)*

normally.

Normal sexual development occurs in three stages: (1) chromosomal (genetic) sex development, (2) gonadal sex development, and (3) phenotypic sex development. Therefore, disorders of sex development and differentiation are classified into three matching groups: (1) sex chromosome disorders, (2) gonadal sex development disorders, and (3) phenotypic sex development disorders. All three groups of disorders result in abnormal sex differentiation and may vary in presentation between genital structure of normal and obscure appearance, and all three groups of disorders may lead to sterility or infertility [11–13].

Chromosomal analysis, anatomical and histopathological definitions of the gonads, and examination of the internal and external genitalia are required for the definite diagnosis of dogs suspected to have disorders of sexual development [11, 14].
