Overview of Canine Hermaphrodite and Pseudohermaphrodite
The word hermaphrodite conjures up visions of a creature half male and half female. A genetic mutation – a freak of nature. But, what exactly is a hermaphrodite?
To understand hermaphrodites, first you need a basic understanding of genetics and the determination of sex. Normal animals have two separate chromosomes that determine their sex, one from the mother and one from the father. Females are designated as XX and males are XY. When an egg is developed, each one has one X chromosome. The sperm can have either one X or one Y. When the sperm and egg are joined at conception, the chromosomes of the egg and sperm are joined together. The resulting embryo is either XX or XY (female fetus or male fetus, respectively). Hermaphrodites occur when chromosomal abnormalities occur and the normal XX or XY does not occur.
All embryos are first developed with gonads that are not specific. Depending on testosterone levels in the developing fetus, the gonads with become testes or ovaries. In embryos with an XX chromosome combination, the resulting fetus will normally develop as female – due to a lack of testosterone, which is produced only when there is an XY combination. Without sufficient testosterone, testes do not form and the ovaries develop by default. In XY embryos, testosterone is secreted and the male genitalia develop and the female genitalia do not.
This normal genital development does not occur in the hermaphrodite. In very rare instances, the developing fetus has a combination of XX and XY chromosomes. More commonly, true hermaphrodites have XX chromosomes but do not develop normally. The animal has both ovaries and testes. This ovary and testicle combination can occur in three separate ways:
- One side has an ovarian/testicle combination organ and the other side has either a normal ovary or normal testicle.
- Each gonad can be a combination of an ovary and testicle, called an ovotestis.
- There can be an ovary on one side and a testicle on the other.
- The amount of testicular tissue in the true hermaphrodite will determine how masculine or feminine the external genitals will appear. It will also determine the development of a uterus.
Of all the intersex cases in dogs, 25 percent are true hermaphrodites. The pet may appear to have a large clitoris but otherwise normal female genitals. Others may have what appears to be a small but otherwise normal penis. Often, the testicles or ovotestis remain within the abdomen and do not descend into the scrotal sacs. Sometimes, the pet is never diagnosed as a hermaphrodite and lives life with few problems. Typically, female dogs do not exhibit heat cycles and do not reproduce.
So, if only 25 percent of intersex cases are true hermaphrodites, what are the other 75 percent? In addition to true hermaphrodites, male and female pseudohermaphrodites and unclassified cases can be diagnosed.
Pseudohermaphrodites are cases when the chromosomes and the gonads match but the external genitals do not. For example, a dog has an XX chromosome and ovaries but also has a penis. Pseudohermaphrodites are divided into two categories, male and female. The most common dog breeds affected with pseudohermaphroditism are miniature schnauzers, poodles and Pekingnese.
Female Pseudohermaphrodite Dogs
Female pseudohermaphrodites have XX chromosomes and ovaries but the internal and external genitals appear masculine due to excess amounts of testosterone. In mild cases, the pet may just have an enlarged clitoris and otherwise appear normal. In more severe cases, the pet may have a normal appearing penis and even a prostate. Usually, female pseudohermaphrodites occur when testosterone-type medications or progesterone are given to the mother during pregnancy. Ovariohysterectomy is recommended to eliminate the risk of uterine or ovarian disease. These dogs are often sterile but should not be bred, even if fertile.
Male Pseudohermaphrodite Dogs
Male pseudohermaphrodites have XY chromosomes and testicles but the genitals appear feminine. Some dogs have vestigial oviducts and uterus with male appearing external genitals. The testicles may be descended into the scrotum or may remain in the abdomen. This most often occurs in miniature schnauzers. In cases with a normal appearing penis and descended testicles, these animals may not be diagnosed unless abdominal surgery is performed and the vestigial female organs are found.
The last category of abnormal gonadal development is the unclassified group. This is used as a catchall for those intersex animals that do not fit into the above categories. These are diverse and rare and take extensive testing to determine the exact chromosomal sex and developmental abnormalities that have occurred.