Disorders of Reproductive Tract Development

Question 1

Define cryptorchidism

Answer 1

Absence of one or both testes within the scrotum

Question 2

What are some other names for the cryptorchid horse?

Answer 2

Ridglings, rigs, high flankers

Question 3

What is the most common developmental disorder of the horse?

Answer 3

Cryptorchidism

Question 4

What are three hormonal tests that may be used in the diagnosis of a cryptorchid horse?

Answer 4

Baseline testosterone + hCG stimulation test
Total estrogens (inn horses over 3 y/o)
AMH

Question 5

Baseline/Pre hCG testosterone in a normal stallion

Answer 5

500 - 1000+ pg/ml

Question 6

Baseline/pre-hCG testosterone in cryptorchid stallions

Answer 6

100 to 500 pg/mL

Question 7

Baseline/pre-hCG in geldings

Answer 7

< 50 pmg/mL

Question 8

What are some estimates regarding chromosome disorders in the horse?

Answer 8

0.1-3%

Question 9

What is the most common chromosomal abnormality in the mare?

Answer 9

63,X (63,XO; X chromosome monosomy)

Question 10

Describe some features of a 63,X horse?

Answer 10

small inactive ovaries
under developed uterus and cervix 
infertile
no behavioral estrus or estrous cycles
normal vulva, clitoris, vaginal vault
Some may be smaller in stature

Question 11

What is mosiacism? Give an example of a karyotype in the mare and stallion.

Answer 11

Refers to the presence of more than one population of cells within a single individual.

Mare: 63, X/ 64, XX
Stallion: 63 X/64, XY; 64,XX, 64,XY

Question 12

What is a male pseudohermaphrodite?

Answer 12

Male gonads

External female phenotype

Question 13

What is a female pseudohermaphrodite?

Answer 13

Female gonads

External male genitalia

Question 14

What is a true hermaphrodite?

Answer 14

Internal male and female gonads; ovotestes

Question 15

Persistent Mullerian Duct Syndrome is more common in what canine breed?

Answer 15

Miniature Schnauzer

Question 16

What happens in a case of freemartinism in regards to the placenta?

Answer 16

Placental anastomosis of blood vessels allows for exchange of testosterone and AMH from the male fetus to the female fetus

Question 17

Which fetus is effected in the case of freemartinism? What effects are seen?

Answer 17

Female fetus
Hypoplastic ovaries
Underdeveloped Mullerian ducts
Wolffian duct tissues
Underdevelopment of female external genitalia