Disorders of sexual differentiation

Question 1

What are the three groups of disorders of sexual differentiation?

Answer 1

1) Gonadal dysgenesis - Sexual differentiation is incomplete. Usually missing SRY in male, or partial or complete deletion of second X in female. Also used as a general description of abnormal development of the gonads.
2) Sex reversal - Phenotype does not match genotype, i.e. may be male genotypically but externally look like a female.
3) Intersex - Have some components of both tracts or have ambiguous genitalia. Sex of infant difficult to determine.
- Patients prefer to be known as someone with a ‘disorder of sexual differentiation’ or DSD.
- Terms such as ‘pseudohermaphrodite’ and, ‘testicular feminisation’ are now obsolete.

Question 2

Describe the pathophsyiology androgen insensitivity syndrome (AIS)?

Answer 2

• Testosterone is made but has no effect in an XY individual
• There will be SRY, so the testes form. Sertoli cells and Leydig cells will be produced. Therefore, AMH and testosterone will both be produced. The Mullerian ducts regress.
• No differentiation of Wolffian ducts = Wolffian ducts require testosterone, which is present, but the androgen receptor is insensitive (not detecting the androgen; not functioning).
• No external male genitalia = Testosterone can be converted to DHT, but the DHT is binding to the same receptor as testosterone (androgen receptor). Both testosterone and DHT bind to the same androgen receptor and, in androgen insensitivity syndrome, that receptor is not working for various reasons (maybe they don’t bind or maybe the receptor doesn’t transmit the signal), but it is insensitive to androgen.
• There will be no internal genitalia and the external will be feminised. The external genitalia relies on DHT, which binds to the same androgen receptor as testosterone.

Question 3

How do patients with complete Androgen Insensitivity Syndrome (AIS) present?

Answer 3

• Complete AIS has an incidence rate of 1 in 20,000 (46XY)
• This is a condition where the patient may not know (at least until puberty), unless it is an incidental finding, e.g. from an operation or genetic test
• Undescended testes.
• No uterus or fallopian tubes
• External genitalia appear female - abbreviated blind vaginal pouch.
• Usually present with primary amenorrhoea. Lack of body hair is a clue.
• Ultrasound scan and karyotype with male levels of androgens.
• Hormonal puberty may be feminizing without intervention due to aromatization of endogenous androgens to estrogens. Lacking response to androgen.
• Sex assignment and rearing almost always female.
• Differentiation of gender role and identity usually feminine. In adulthood, sexuality often conforms to typical heterosexual female expectations.

Question 4

How do patients with partial Androgen Insensitivity Syndrome (AIS) present?

Answer 4

• Partial AIS - incidence unknown - spectrum (46XY)
• More commonly, it is a partial syndrome. There is more than one androgen receptor and there can be various levels of sensitivity to androgens.
• Spectrum of phenotypes including almost normal female external genitalia through ambiguous genitalia (perineoscrotal hypospadias, microphallus, cryptorchidism).
• Minor genital deviations go unnoticed or may be surgically repaired.
• At puberty, development of male secondary characteristics may not be very pronounced. In some cases, pubertal gynecomastia (androgen/estrogen ratio) or ambiguous genitalia surgically corrected. Androgen therapy in some cases.
• Majority of individuals develop an identity commensurate with their assigned gender - around 20% desire to change gender usually in adolescence or adulthood.
• Puberty can be very distressing for a patient who may look more masculine as their testosterone levels dramatically increase (may exceed the threshold for the androgen receptor to work)
• Common practice is to wait and let the patient decide their gender (not to reassign their gender too early). Want what is right in the interest of the patient (psychosocial).

Question 5

What happens if XY male is unable to make or respond to AMH in utero?

Answer 5

• Persistent Mullerian duct syndrome
• Testes form and there are Sertoli cells, but they either fail to make AMH or the AMH that is made does not bind to the receptor (Receptor does not function).
• Mullerian ducts remain.
• Differentiation of Wolffian ducts and masculinised external genitalia. Leydig cells and testosterone function normally, so there is differentiation and growth of the Wolffian structures. Testosterone is also converted to dihydrotestosterone (DHT). The male genitalia will be normal PLUS Mullerian structures.

Question 6

What is the difference between PMDS type I and II?

Answer 6

• Persistent Mullerian duct syndrome
• PMDS type I results from mutations of the gene for AMH on chromosome 19.
• PMDS type II results from mutations of the gene for the AMH receptor (AMH-RII) on chromosome 12.
• Both autosomal recessive conditions (transmitted in the classic Mendelian fashion) with expression usually limited to XY offspring.

Question 7

Describe the common clinical presentations of Persistent Mullerian duct syndrome.

Answer 7

• 60–70% of cases have intra-abdominal Mullerian structures and testes in a position simulating that of the ovaries
• 20–30% have one testis in a hernial sac or scrotum together with Mullerian structures.
• 10% have both testes located in the same hernial sac (transverse testicular ectopia) along with the uterine tubes and/or uterine structures.
• All have increased risk of malignant transformation.
• In some cases, patient can have undescended testes with Mullerian structures. Otherwise, one testis can descend into the scrotal sac while Mullerian structures are present. Sometimes, both testes will end up in one scrotal sac while attached to some kind of Mullerian structure.
• One of the problems with this is a risk of testicular tumours in these undescended testes. Likely need to surgically intervene; retrieve the testes and position them back in the scrotum (wanted for fertility and the testosterone they produce).

Question 8

What are the treatments of Persistent Mullerian duct syndrome

Answer 8

• Surgery (orchiopexy) to retrieve the testes and position them in the scrotum. If testes cannot be retrieved, testosterone replacement at puberty is an option.
• Removal of uterus dissection of Müllerian tissue away from the vas deferens/epididymis.
• Laparoscopic hysterectomy may prevent the occurrences of neoplastic tissue formation.
• One of the problems with this is a risk of testicular tumours in the undescended testes. Likely need to surgically intervene; retrieve the testes and position them back in the scrotum (wanted for fertility and the testosterone they produce). If they can’t be retrieved, testosterone replacement therapy can be given at puberty. Usually want to remove the uterus and dissect out the malaria and tissue if possible (may even come to laparoscopic hysterectomy to prevent any kind of neoplastic tissue/cancer transformation in this tissue).

Question 9

Summary

Answer 9

• Correct sexual differentiation requires genetic, anatomical and endocrine components.
• Disorders are rare, but have allowed scientists to understand the requirements for normal development.
• Diagnosis and treatment of conditions of abnormal sexual differentiation requires a specialist team.
• Long-term functioning of the person now the primary issue rather than immediate ‘corrective’ surgery.
• Need to be sensitive; consider all the philosophical and social aspects of it as well as the science.

Question 10

What condition results from testosterone being made in an XY individual but not DHT?

Describe the pathophysiology.

Answer 10

• 5-α-reductase deficiency
• Not converting testosterone to DHT = problem with the 5-α-reductase gene
• 5-α-reductase may be present in the genital skin, but not functioning (either mutated, not working or not present). There is no DHT, so there is normal internal genitalia (undescended testes perhaps) but the external genitalia will look female (or ambiguous).
• Testes form and make AMH, so Mullerian ducts regress.
• Wolffian ducts develop as testosterone is present.
• No external male genitalia.

Question 11

How do patients with 5-α-reductase deficiency present clinically?

Answer 11

• Incidence varies enormously (46XY)
• Testes form, AMH acts, testosterone acts. Internal structures form. External male structures do not fully develop. Again, there is a lot of variation in presentation.
• May appear mainly female or may have ambiguous genitalia such as labioscrotal folds or clitoridean penis. The degree of the enzyme block varies and so therefore does the presentation.
• Need to assess potential as high testosterone level which will occur at adrenarche and puberty may induce virilisation (if partial block). If it is a partial block, when testosterone levels rise dramatically at puberty, it might be enough to exceed the threshold and start virilization. They may begin with primary female-looking/ambiguous genitalia as a child and then, at puberty, they may produce enough DHT to develop and masculine their genitalia. Important to think about the patient (patient-centred); what does the patient want, how do they feel (nature-nurture;psychosexual). Can’t rush the process because feelings can change with hormone levels.
• Both testosterone and dihydrotestosterone (DHT) are capable of masculinising the brain in non-human primates so some brain masculinisation in utero possible with this condition.

Question 12

What happens if 45 XO? Describe the pathophysiology of this condition.

Answer 12

• Turners syndrome = 1:3000
• Ovaries because there is so Y chromosome for the SRY gene
• No AMH, so Mullerian ducts are present (uterus and uterine tubes). No Wolffian ducts as there is no Sertoli cell or testosterone.
• External female genitalia

Question 13

How do patients with Turner’s syndrome clinically present?

Answer 13

• XO have failure of ovarian function. ‘Streak’ ovaries = ovarian dysgenesis; illustrates that we need two X’s for ovarian development.
• This is interesting as men only have one X chromosome and only one X chromosome is expressed in any given cell in females too (can vary which one it is). Pseudoautosomal genes are genes that are expressed like autosomal genes (non sex genes). There are a few genes on the repressed X that are being made which seem to be important in normal development. Therefore, both X chromosomes are needed, even though only a few genes are being used on the suppressed one for normal development. In a way, all women are mosaics, in the sense that it’s a different X chromosome expressed in each of their cells.
• Turner syndrome does illustrate that the second X chromosome is necessary for normal development. Some genes on the second repressed chromosome are not in fact repressed; these active chromosomes are mainly the pseudoautosomal regions.
• There is such a big variation in the presentation of Turner syndrome because it depends on when the second X is lost. If the second X is lost at one of the first cell divisions in the early embryo, then every cell in the body will just have one X . However, if it happens later during embryogenesis, only the descendants of the cells where it was lost will only have one X chromosome. Some women with Turner syndrome may have two X chromosomes in some of their cells but in a severe case, all cells may only have one. This explains the huge variation.
• Uterus and tubes are present, may be small or other defects in growth and development. Wide spectrum of phenotypic disorders and severity (some are mostly unaffected (fertile), while others are severely affected with dysgenesis of the uterus and ovaries, for example).
• May be fertile, many have mosaicism. Female gender.
• Hormone support of bones and uterus (hormone replacement therapy).

Question 14

What is the most common treatment for patients with Turner’s syndrome?

Answer 14

• Hormone support of bones and uterus (hormone replacement therapy).
• There is such a big variation in the presentation of Turner syndrome because it depends on when the second X is lost. If the second X is lost at one of the first cell divisions in the early embryo, then every cell in the body will just have one X . However, if it happens later during embryogenesis, only the descendants of the cells where it was lost will only have one X chromosome. Some women with Turner syndrome may have two X chromosomes in some of their cells but in a severe case, all cells may only have one. This explains the huge variation.
• May be fertile, many have mosaicism. Female gender.

Question 15

What is the most common cause of an XX female being exposed to high levels of androgens in utero?

Answer 15

• Congenital adrenal hyperplasia is most common cause = 1:15,000.

Question 16

Describe typical steroidogenesis.

Answer 16

• Cholesterol has three six-sided rings, a five-sided ring and a carbon chain.
• All of the steroids are cholesterol with the carbon chain reduced to different lengths.
• The progestogens are cholesterol with 21 carbon atoms (differ by the hydroxyl/oxygen group positionings). Many enzymes listed are involved in altering the groups.
• Removing two more carbons produces the androgens. The androgens have three six-sided rings and a five-sided ring (19 carbons). The difference between all of the androgens is again the positioning of the extra groups. The enzymes move the groups around the rings.
• Removing one more carbon, leaving 18 carbons, produces the oestrogens. There are three types of oestrogen that differ by their hydroxyl groups, e.g. oestradiol (E2) has two, oestrone has one (E1) and oestriol (E3) has three. In the menstrual cycle, it is mainly oestradiol (E2), but the others are also seen (E3 in pregnancy).
• The enzyme that clips off the extra carbon from androgen to oestrogen, in aromatisation) is called aromatase.
• The progestogens, the androgens and the oestrogens are the sex steroids. These three steroids are made in the testis and in the ovary. It brings in cholesterol, there is a side chain cleavage enzyme that clips off that chain and progestogens are produced. The other enzymes can then act to produce the other sex steroids.
• Steroidogenesis includes the adrenal glands (pyramid-shaped glands on top of the kidney that make additional steroids). As well as making the sex steroids, the main purpose for the adrenal glands is to produce aldosterone and cortisol. Progesterone is made first and then subsequent steps convert it into aldosterone. It still has 21 carbon atoms like the progestogens, but it has additional groups around the rings. Required to recover salt, potassium and water; used in the RAAS system. Cortisol is a glucocorticoid. Again, it consists of 21 carbon atoms; they are both made from the progestogens produced from cholesterol. This affects stress and the glucose response etc. 21-hydroxylase and 11-beta hydroxylase are important enzymes in this process.

Question 17

Describe the pathophysiology of congenital adrenal hyperplasia (include steroidogenesis and the hypothalamic-pituitary-adrenal axis).

Answer 17

• The foetus takes in cholesterol and converts it to progestogen as a raw material. It is missing the enzyme to then convert this to aldosterone or cortisol.
• With congenital adrenal hyperplasia, 21-hydroxylase deficiency is the most common cause.
• Hypothalamus produces CRH which stimulates the pituitary to secrete adrenocorticotropic hormone (ACTH). This acts on the adrenal glands to stimulate rapid uptake of cholesterol into the adrenal cortex. Upregulates cholesterol side-chain cleavage enzyme (P450scc). Increases glucocorticoid secretion. A foetus with congenital adrenal hyperplasia tries to do this, but can’t make aldosterone or cortisol. There is no negative feedback from cortisol in the HPA axis, so there are increased amounts of CRH and ACTH.
• Increased CRH and ACTH stimulate cholesterol uptake and adrenal cortex activity. Cortisol itself doesn’t rise because of enzyme block.
• There is no negative feedback from cortisol. Without any negative feedback, there are increased amounts of CRH and increased amounts of ACTH in an attempt to make cortisol. ACTH trying to drive the production of cortisol causes an upregulation in cholesterol side-chain cleavage enzyme. More cholesterol is brought in, the side chain is removed and progestogen levels start to rise.
• The progestogens can’t be converted into aldosterone and cortisol, so they get converted into androgens. Therefore, androgen levels start to rise. In the female embryo, there are very primitive granulosa cells, but they are not yet expressing aromatase (not until puberty) so can’t be converted into oestrogen. There is a build up and release of androgens.

Question 18

How does Congenital adrenal hyperplasia (CAH) present clinically?

Answer 18

• 1:15,000 (XX).
• No SRY (ovaries form instead), so no testes and then no AMH.
• Mullerian ducts remain. There is no AMH, so she will have a uterus, tubes and the upper third of her vagina.
• However, the Wolffian ducts can be rescued by the androgens produced from her adrenal glands (don’t regress). Also, there is 5-α-reductase present. The androgens are converted to DHT and the external genitalia is masculinised. The androgen levels may not totally rescue the wolffian ducts, but can rescue some parts of them (some wolffian duct structures); the completeness of the enzyme block varies.
• Masculinised external genitalia, but androgen levels not usually high enough to rescue Wolffian ducts.
• An ultrasound shows the adrenal glands getting bigger in the baby girl as she tries to make cortisol/aldosterone. All this does is produce more testosterone and other androgens.
• Completeness of the enzyme block varies. May have developed Wolffian structures and ambiguous masculinised external genitalia or hirsutism.
• Early studies suggested that XX patients assigned as girls developed female gender identity, but with more masculine childhood behaviour and lower maternal interest as adults. – may androgen-related or may be societal influence…
• Also in CAH need to be aware of possibility of ‘salt-wasting’ due to lack of aldosterone, this can be lethal. Aldosterone is required to recover salt, potassium and water; used in the RAAS system. Struggle making aldosterone, which can be life threatening; danger of salt-wasting disease, losing a lot of potassium.
• Treatment with glucocorticoids to correct feedback.