Endocrinology Flashcards
What are causes of primary amenorrhea?
- Gonadal dysgenesis (ex turner syndrome)
- Mullerian dysgenesis (Mayer-Rokitansky-Kuster-Hauser syndrome).
- Androgen insensitivity syndrome
What is gonadal dysgenesis?
Perrault syndrome: 46 XX – gonadal dysgenesis and sensorineural deafness. No puberty or breasts but have uterus 2/2 absence of AMH.
Swyer syndrome (SRY mutation): 46 XY; gonadal dysgenesis. No puberty or breasts but have uterus 2/2 absence of AMH. appears female, streak ovaries
What is Mullerian dysgenesis?
46 XX, normal breast/external genitalia/pubic/axillary hair. Absent vagina without cervix, usually rudimentary uterus at best. ddx: MRI/US when primary amenorrheic
Non-surgical approach=1st line (vaginal dilators).surgical approach: create neovagina using skin graft.
Key words: MRKH, scoliosis, renal anomalies
What is androgen insensitivity syndrome?
X-linked recessive. 46 XY
- Testes make testosterone and AMH. Androgen receptor not sensitive so no internal or external genitalia.
Puberty: high estrogen 2/2 peripheral conversion from testosterone causes feminization (BREASTS) bc no androgen action to oppose it.
Phenotypic female w/ primary amenorrhea, absent uterus, has testes (inguinal hernia) no pubic/axillary hair, high testosterone.
incr risk testicular cancer: bilateral gonadectomy post-puberty to prevent.
Differs from Mullerian dysgenesis: mullerian dysgenesis have normal axillary/pubic hair, short vagina, normal testerosterone, 46 XX
What are facts on Mullerian dysgenesis?
-eval for congenital anomalies bc 53% pts have them, of urinary tract and skeleton (renal anomalies, scoliosis)
- PE: normal breasts, external genitalia, body hair.
What is initial lab evaluation of patient with primary amenorrhea?
FSH and karyotype to rule out Turner syndrome (most common cause). Elevated FSH, 45X.
Turner: short stature, normal vagina/cervix/uterus, delayed puberty 2/2 hypogonadism, no boobies!.
What is congenital adrenal hyperplasia?
CYP17A1 deficiency. autosomal recessive. heterogenous form
- similar to mullerian dysgenesis:
- overproduction of aldosterone=HTN, hypoK
- If 46 XX: uterus, vagina, fused labioscrotal folds, enlarged clitoris
- If 46 XY: female external genitalia, short vagina, no uterus, intra-abdominal testes (need gonadectomy)
ddx: high deoxycorticosterone, low cortisol, androgens, estrogen
- tx: dexamethasone
How does TSH change throughout pregnancy?
TSH decreases in 1st trimester bc B-HCG stimulates TSH-R causing incr T4.
TSH increase in 3rd trimester 2/2 placental growth
T4 transferred to fetus throughout pregnancy, affects fetal brain development. 30% T4 in fetus at delivery is maternal in origin.
When does the fetus start synthesizing iodine?
Fetus starts concentrating iodine and synthesizing thyroid hormone at 12 weeks!
What is a prolactinoma?
Macroadenoma is >1cm. From anterior pituitary.
Premenopausal: diagnosis if prolactin >30, postmenopausal >40. If >200, almost definitely prolactinoma
Tx: Dopamine agonist (Cabergoline>bromocriptine), ovulation induction if desire fertility, surgery only if meds don’t work.
What is Swyer syndrome?
Type of gonadal dysgenesis=no ovaries 2/2 deficiency of SRY gene
- XY chromosome but LOOK FEMALE! normal female reproductive organs, including a uterus, fallopian tubes, and vagina BUT NO OVARIES. DDX in puberty when menses don’t occur. - -
- Incr risk of germ cell tumors.
- Normal stature/phenotype, no secondary sex characteristics, high FSH, elevated testosterone.
- Need gonadectomy!!
What is hyperandrogenism in adolescents?
Differential ddx:physiologic hyperandrogenism of puberty, idiopathic hyperandrogenism, PCOS. More rare: non-classic CAH, androgen-secreting tumors, hypothyroid, Cushing, severe hyperprolactinemia
What is management of hyperandrogenism in adolescents?
Androgens originate from 3 places: ovarian theca, adrenal cortex, end organs by peripheral conversion
Main androgens: dehydroepiandrosterone, dehydroepiandrosterone sulfate (DHEAS), androstenedione, testosterone, dihydrotestosterone.
In women, testosterone mostly bound by sex-hormone binding globulin and albumin, so only 1% free testosterone.
5-alpha reductase: converts testosterone to potent dihydrotestosterone
Ddx:
If regular menses -> Labs (free/total T, DHEAS, 17-OHP)
If irregular menses: LH, FSH, prolactin, TSH, free/total T, DHEAS, 17-OHP
Ovarian tumor if testosterone >200, adrenal tumor if DHEAS>700, CAH if 17-OHP >200
What is thyroglobulin?
protein made by the follicular cells of the thyroid gland. It is used by the thyroid gland to produce T3 and T4.
What is tyrosine?
Tyrosine is an amino acid that is used as a precursor for the synthesis of the catecholamines dopamine (DA) and norepinephrine (NE)
- Thyroxine (T4) is produced through the iodination of tyrosine
- does NOT cross placenta
