Effect of long-term administration of cross-sex hormone therapy on serum and urinary uric acid in transsexual persons.
BACKGROUND
Transsexual persons afford a very suitable model to study the effect of sex steroids on uric acid metabolism.


METHODS
This was a prospective study to evaluate the uric acid levels and fractional excretion of uric acid (FEUA) in a cohort of 69 healthy transsexual persons, 22 male-to-female transsexuals (MFTs) and 47 female-to-male transsexuals (FMTs). The subjects were studied at baseline and 1 and 2 yr after starting cross-sex hormone treatment.


RESULTS
The baseline levels of uric acid were higher in the MFT group. Compared with baseline, uric acid levels had fallen significantly after 1 yr of hormone therapy in the MFT group and had risen significantly in the FMT group. The baseline FEUA was greater in the FMT group. After 2 yr of cross-sex hormone therapy, the FEUA had increased in MFTs (P = 0.001) and fallen in FMTs (P = 0.004). In MFTs, the levels of uric acid at 2 yr were lower in those who had received higher doses of estrogens (P = 0.03), and the FEUA was higher (P = 0.04). The FEUA at 2 yr was associated with both the estrogen dose (P = 0.02) and the serum levels of estradiol-17beta (P =0.03). In MFTs, a correlation was found after 2 yr of therapy between the homeostasis model assessment of insulin resistance and the serum uric acid (r = 0.59; P = 0.01).


CONCLUSIONS
Serum levels of uric acid and the FEUA are altered in transsexuals as a result of cross-sex hormone therapy. The results concerning the MFT group support the hypothesis that the lower levels of uric acid in women are due to estrogen-induced increases in FEUA.
Yahyaoui
R
R
Clinical Laboratory, Department of Endocrinology, Andalusian Gender Team, Carlos Haya University Hospital, Avenida Moliere 22, Malaga, Spain. yayiobo@hotmail.com
Esteva
I
I
Haro-Mora
J J
JJ
Almaraz
M C
MC
Morcillo
S
S
Rojo-Martínez
G
G
Martínez
J
J
Gómez-Zumaquero
J M
JM
González
I
I
Hernando
V
V
Soriguer
F
F
D000328:Adult; D001786:Blood Glucose / Q000032:analysis; D004305:Dose-Response Relationship, Drug; D004958:Estradiol / Q000097:blood; D005260:Female; D005500:Follow-Up Studies; D012739:Gonadal Steroid Hormones / Q000008:administration & dosage / Q000627:therapeutic use*; D006801:Humans; D007328:Insulin / Q000097:blood; D007333:Insulin Resistance; D008297:Male; D013997:Time Factors; D014189:Transsexualism / Q000097:blood / Q000188:drug therapy* / Q000652:urine; D014527:Uric Acid / Q000097:blood* / Q000652:urine*
D001786:Blood Glucose; D012739:Gonadal Steroid Hormones; D007328:Insulin; D014527:Uric Acid; D004958:Estradiol