Abstract
Introduction: Acromegaly results from the chronic and persistent elevation of growth hormone (GH) circulating levels. Several isoforms of the receptor of GH have been identified; one contains exon 3 giving rise to the full form of the GHR or full-length (fl), and another one lacking this exon (d3). This isoform heterogeneity results in the following genotypes: homozygous fl, heterozygous d3/fl and homozygous d3. Objective: To determine if the GHR genotype influences the clinical and/or biochemical expression of acromegaly. Methods: Forty-nine (30 women/19 men) acromegalic patients and forty-one control subjects (22 women/19 men), aged 30 to 76 years, who attended the Endocrinology Department of a Hospital in Buenos Aires, Argentina, were evaluated. Genotyping of the GHR was performed by a multiplex polymerase chain reaction (GAP-PCR). Clinical data were recorded, and general biochemical and hormonal determinations were carried out (IGF-1, GH and PRL). To measure tumor dimension, Magnetic Resonance Imaging (MRI) of the sellar area was performed in all patients. Results: The frequency of the genotypes was 61.2% homozygous fl, 34.7 % heterozygous d3/fl and 4.1 % homozygous d3 in acromegalic patients and 48.8% homozygous fl, 41.5% heterozygous d3/fl and 9.7% homozygous d3 in control subjects. The frequency of the genotypes in the studied population was in Hardy-Weinberg equilibrium (p = 0.8878). In this group of acromegalic patients, we did not observe any associations of the genotypes with the body mass index (BMI), the presence of micro or macroadenomas, the response to treatment, the presence of hypertension, diabetes or dyslipidaemia, neither with GH, IGF-1 or PRL levels. Conclusion: The present study confirms that the distribution of the allele coding for the isoform without the exon 3 of GHR in this group of acromegalic patients is similar to that observed in healthy subjects and to that reported in the literature. On the other hand, the presence of the polymorphism of the GHR is not related to BMI, tumor size, response to treatment, metabolic alterations or to hormonal levels in this group of acromegalic patients evaluated.