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Clin Endocrinol (Oxf). 2004 Jan;60(1):36-40.

The first homozygous mutation (S226I) in the highly-conserved WSXWS-like motif of the GH receptor causing Laron syndrome: supression of GH secretion by GnRH analogue therapy not restored by dihydrotestosterone administration.

Author information

1
Unidade de Endocrinologia do Desenvolvimento, Laboratorio de Hormonios e Genetica Molecular LIM/42, Disciplina de Endocrinologia, Hospital das Clinicas, Sao Paulo, Brazil. alexj@usp.br

Abstract

OBJECTIVE:

The study describes for the first time, a homozygous mutation in the WSXWS-like motif of the human GH receptor (GHR) in a patient with Laron syndrome and describe laboratory data during treatment with GnRHa to suppress puberty and dihydrotestosterone (DHT).

PATIENTS:

A 16-year-old boy at Tanner puberty stage 2 with Laron syndrome was born SGA to consanguineous parents, presented severe growth retardation, obesity and micropenis.

METHODS AND MEASUREMENTS:

GHR coding region was sequenced. GH, GHBP, IGF-I and IGFBP-3 were determined before, during and after GnRHa and DHT treatment.

RESULTS:

A homozygous mutation in exon 7, replacing serine by isoleucine in codon 226 was identified. S226 is the last serine belonging to the WSXWS-like motif in GHR. No specific effect of S226I mutation in heterozygous state was observed. Laboratory data at the prepubertal age showed markedly high GH, low GHBP, IGF-I and IGFBP-3 levels. Re-evaluation at pubertal age showed normal basal serum IGFBP-3 levels and low but near normal IGF-I levels. We also noticed a sustained decrease in GH, IGF-I and IGFBP-3 levels after blocking puberty, which was not affected by short- and long-term DHT treatment. Pubertal hormonal profile was re-established after the GnRHa therapy was discontinued to allow the reactivation of the gonadal axis.

CONCLUSION:

The homozygous mutation S226I in WSXWS-like motif of GHR causes GH insensitivity. The decrease in IGF-I and IGFBP-3 levels after GnRHa therapy, which was not reversed with DHT administration, suggests that sex steroids have, through oestradiol, a GH-independent action on IGF-I and IGFBP-3 levels. A direct effect of GnRHa on GH secretion cannot be excluded.

PMID:
14678285
[Indexed for MEDLINE]

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