Background Leptin is an adipocyte-derived hormone. The plasma level of leptin is elevated in obesity and decreased in emaciation. It is involved in the neuroendocrine regulation of pituitary gland function.

Aim of the work The present work was carried out to study the histological changes in the pars distalis of the pituitary gland after an injection of leptin in female albino rats.

Materials and methods Thirty just-weaned immature female albino rats (22 days) were divided into two groups: group I included 10 animals and served as a control group and group II included 20 animals that received a daily subcutaneous injection of 5µg leptin up to the end of the experiment. The females were subjected daily to vaginal smear. After the maturation was established, rats from each group were again subdivided into groups a and b, which were sacrificed 4 and 20 days after puberty, respectively. The pituitary glands were dissected and specimens were prepared for electron microscopic and immunohistochemical assessment.

Results Leptin injection induced various changes in the pars distalis of the pituitary gland. Some cells had deeply stained nuclei and vacuolated cytoplasm. There was a statistically significant increase in the number of positive p53 antibody immunostained cells in the leptin-treated group, especially after 4 days of leptin injection. The most affected cells were somatotrophsthyrotrophs, and gonadotrophs. They showed features of hyperactivity, with the appearance of some apoptotic cells. Later, necrotic changes such as pyknotic nuclei, ballooned mitochondria with destroyed cristae, and dilated rough endoplasmic reticulum were observed.

Conclusion and recommendations Prepubertal increase in leptin led to histological changes in some cells of the pars distalis. It is recommended to avoid increase in body weight, especially at a young age.