Leptin influences mammary carcinogenesis in hypothyroid rats.

LÓPEZ FONTANA C; MASELLI ME; SASSO CV; SEMINO S; ZUBIRÍA MG; JAHN GA; CARON RW

San Juan

Congreso; II Reunión Conjunta de Sociedades de Biología de la República Argentina; 2011

Sociedad de Biología de Cuyo

We aimed to determine the influence of the hormonal background induced by hypothyroidism on mammary carcinogenesis. Female Sprague-Dawley rats were treated per os with a single dose of DMBA (15mg/rat) at 55 days of age and divided into two groups: euthyroid (EUT, n=17) and hypothyroid rats (HYPO, 0.01% PTU in drinking water, n=16). All the animals were weighted weekly and observed until the appearance of the first palpable tumor. The latency, incidence and progression of tumors were determined in the two groups. Whole blood samples and a piece of normal mammary gland and tumor were taken for hormone determinations and histological analyses. Statistical analysis was performed by Student T test and Chi square (IC>95%). HYPO showed significantly retarded growth and reduced levels of circulating GH. The latency of onset of tumors was longer, and the incidence and tumor growth rate were lower in HYPO than in EUT. The histopathology was similar in the two groups. No statistical differences were observed in prolactin levels. However, circulating leptin was significantly lower in HYPO than EUT even though body fat mass was similar in both groups. To note, leptin levels were higher in HYPO rats that developed mammary tumors than in non tumoral HYPO. In conclusion, low serum leptin concentrations may be responsible of the decreased carcinogenesis observed in HYPO rats.