Mehl. Androgen insensitivity+ 5a reductase Flashcards
Mehl. kariotype?
46XY karyotype; female phenotype.
Mehl. Defect in …?
Defect in androgen receptor.
Since DHT is needed for external male development, the patient appears female.
Mehl. Testosterone and DHT levels?
Testosterone and DHT are normal or elevated due to decr. negative-feedback at the hypothalamus and anterior pituitary -> incr. LH production -> incr. testicular androgen production.
Mehl. The testes in AIS are usually located within ???
abdomen or inguinal canal.
Mehl.
Even though there is resistance to androgens, testes still develop because the the SRY gene on the Y chromosome induces differentiation of the primitive gonads into testes. This differentiation isn’t dependent on androgens.
.
Mehl. Testes produce Müllerian-inhibitor factor, so there is no uterus or Fallopian tubes in AIS.
.
Mehl. Even though the gonads also produce androgen, since we have resistance to it, the ….karyptype?
karyotypic male appears female (i.e., phenotypically female).
Mehl. Breast development is Tanner ?
4-5
Mehl. pubic/axillary hair is Tanner?
1
Mehl.
15-year-old girl is brought to the physician by her mother for not yet having a menstrual period + vagina ends in blind pouch + pubic/axillary hair is scant/absent. Dx? NEXT STEP?
AIS
Next best step = ultrasound first if listed, then karyotype.
Mehl. incr risk for what repr. tumor?
risk of testicular malignancy (dysgerminoma).
Mehl. what prophylactic surgery is recommended?
risk of testicular malignancy (dysgerminoma), so prophylactic orchiectomy is indicated after puberty (maximizes estrogen effects for phenotypic female development), unless evidence of malignancy is seen prior.
Mehl. 5a reductase deficiency. karyotype?
phenotype in neonates?
46XY karyotype; phenotypically female, or neonate with ambiguous genitalia.
Mehl. 5a reductase deficiency. 5a-reductase is enzyme that converts ….?
Testosterone -> DHT. If there is a deficiency and DHT is decr., male external structures don’t develop, so phenotype is female.
Mehl. 5a reductase deficiency. buzzy CP?
Presents as “phallus (penis) at age 12.” This is buzzy
Mehl. 5a reductase deficiency.
at puberty, the incr. (2 arrows) in testosterone can partially override the enzyme deficiency, leading to threshold production of DHT where male secondary sex characteristics can develop.
.
