Introduction

• Prolonged anestrus following puberty, complete inactivity of ovaries.
• Cause: ovariectomy, age, chronic administration of androgens or progestagens, hypothyroidism, delayed puberty Delayed puberty , idiopathic.
• Signs: primary anestrus = failure to show signs of estrus >24 months of age; secondary anestrus: failure to display signs of estrus 10-18 months after a preceding estrus.

Pathogenesis

Etiology

• Ovariohysterectomy Ovariohysterectomy.
• Systemic abnormalities → debility, eg diabetes mellitus Diabetes mellitus , hyperadrenocorticism Hyperadrenocorticism and hypothyroidism Hypothyroidism.
• Ovarian disorders: ovarian aplasia, progesterone-secreting cysts, auto-immune oophoritis.
• Congenital abnormalities of sexual differentiation.
• Drug-induced anestrus: exogenous administration of progestagens or androgens.
• Ovulatory estrus without accompanying behavioral signs of sexual receptivity (silent heat).
• Pregnancy.
• Delayed puberty Delayed puberty.

Predisposing factors

• See above (congenital, acquired disorders, iatrogenic).

Pathophysiology

• Ovariectomy → lack of ovarian hormones.
• Systemic disease may → hypothalamic-pituitary-gonadal axis abnormality .
• Aging → ovarian senescence not clearly documented in the dog.
• Exogenous androgens or progestogens → chronic suppression of ovarian activity.

Diagnosis

Treatment

Prevention

Outcomes