There are three genetic conditions that can affect female fertility with varying degrees of severity, and there are management options that can result in pregnancy for two of the conditions.
- Turner’s Syndrome
- Androgen Insensitivity Syndrome
- Congenital Adrenal Hyperplasia
Turner’s syndrome is a genetic condition that only affects women, and about 1 in 2000 to 5000 girls are born with it. The syndrome is caused by a complete or partial lack of one of the two sex chromosomes that results in the woman carrying “XO” rather than the usual two X female sex chromosomes and being “XX”.
There are some instances where part of the second X chromosome is present, but this still creates degrees of genetic abnormality. Because of the possible variations involved, a wide range of symptoms are associated with Turner’s syndrome, which means the condition can vary considerably from one person to the next. The impact of Turner’s syndrome on fertility is: i
- Primary amenorrhea (no menstrual bleeding)
- Premature ovarian failure
The definitive test is a chromosome (karyotype) test that shows the absence or reduction in one of the X chromosomes.
Modern advances in fertility medicine have meant that some women with Turner’s syndrome women can get pregnant, with egg donation being an essential part of the IVF because the ovaries of Turner’s syndrome women can’t produce mature eggs.
Because the ovaries aren’t fully developed, estrogen replacement therapy is needed for several months to develop the uterus and its blood supply so they grow enough to support conception and pregnancy. More information is available on the Turner Syndrome Society’s website: www.tss.org.uk
Androgen Insensitivity Syndrome
Androgen Insensitivity Syndrome (AIS) was previously known as “testicular feminisation” and it’s an uncommon condition but causes 10% of all cases of primary amenorrhoea (where a woman never has a period). The underlying genetic reason for this is that although a woman may look perfectly normal in all respects, her cells have XY sex chromosomes, which are the sex chromosomes for a man.
This can happen because the blueprint of all embryos is female, and for a baby to have a “sexual identity” it must respond to the release of sex hormones while it grows in the womb. If there’s little or no sensitivity to male hormones (androgens) during the time when sex organs should develop it leads to AIS, which can happen in two ways:
- Androgen receptors are absent
- The androgen receptors are present, but they fail to function correctly
Either can prevent or reduce the normal masculinisation of the sex organs in a developing XY male baby that typically starts in the seventh week of pregnancy and lasts until a few months after birth. Androgens change the sex organs into a penis and the testes, and XX female babies trigger the release of feminising hormones (estrogens) that promote ovarian and uterine development. With AIS, neither of these options takes place.
Types of AIS
Three categories of AIS reflect the degree of masculinisation of external genitalia:
- Complete Androgen Insensitivity Syndrome (CAIS) involves external genitalia of a typical female
- Partial Androgen Insensitivity Syndrome (PAIS) is when external genitalia are partially (but not entirely) masculinised
- Mild Androgen Insensitivity Syndrome (MAIS) is when external genitalia are close to those of a typical male
The internal gynaecological structures for all women with AIS are different from the norm, as they may have a vagina, but a uterus won’t have formed, making pregnancy impossible. Explaining the full consequences of AIS is beyond the scope of this article.
A karyotype test (a chromosomal analysis) determines a person’s chromosomal makeup to either confirm or exclude AIS. Information on Androgen Insensitivity Syndrome: www.aissg.org
Congenital Adrenal Hyperplasia
Congenital adrenal hyperplasia (CAH) is an inherited disorder of the adrenal glands that affects about 1 in 10,000 to 18,000 newborn babies, and while both sexes are affected, it reduces female fertility more than male fertility.
The critical issue for people with (CAH) is the lack of an enzyme the adrenal gland needs to make cortisol and aldosterone hormones. In the absence of cortisol and aldosterone, the body produces more androgens (male sex hormones) to compensate, which causes male characteristics to appear early (or inappropriately) in life.
Boys won’t have any apparent problems at birth, however, they may appear to enter puberty as early as 2-3 years of age and then develop:
- A deep voice
- Pubic and armpit hair and abnormally early development of male characteristics
- An enlarged penis and small testes
- Well-developed muscles
Girls will usually have normal female reproductive organs (ovaries, uterus and fallopian tubes), but they may also experience:
- Abnormal menstrual periods or a failure to menstruate
- A deep voice
- The early appearance of pubic and armpit hair, which may develop into generally excessive hair growth
- Genitals that look both male and female (ambiguous genitalia) and often appear more male than female
Both boys and girls will be tall as children, but as adults will be much shorter than average.
- Blood tests show high levels of 17-OH progesterone and DHEA sulphate and low levels of aldosterone and cortisol, which indicates congenital adrenal hyperplasia and abnormal salt levels usually accompany this
- Other indicators are urine tests that show abnormal salt levels, along with high levels of urinary 17-ketosteroids and low or normal levels of 17-hydroxycorticosteroids
- X-rays will reveal bones that appear older than average for that person’s age
The goal of treatment is to normalise hormone levels with a daily intake of cortisol (dexamethasone, fludrocortisone, or hydrocortisone), and additional doses of medicine are often needed during stress, severe illness or surgery.