The structure and hormonal activity of the thyroid gland and its capacity to bind (3)H-melatonin were studied in young adult Chinchilla rabbits with pineal gland hypofunction induced by 2-month exposure to constant illumination. After 2 months of constant exposure to light, the experimental animals exhibited signs of the so-called "latent hypothyroidism" and more intense binding of (3)H-melatonin by the thyroid gland. This fact indicated intactness of its receptor system underlying the possibility of restoring activity of the thyroid gland under conditions of melatonin replacement therapy in hypothyroidism induced by chronic melatonin insufficiency.
The pituitary-thyroid axis of young sexually mature rabbits kept under a 24-hour daylight photoperiod was shown to undergo phase-modulated variations of hormonal activity with its initial increase (during the first month) and subsequent progressive decrease (within 2-5 months after the onset of exposure to light). These changes correlated with the time-dependent fall in the blood T3, T4, and TSH levels. Simultaneously, the animals developed pathological changes in the histological structure of the thyroid gland similar to those in patients with secondary or tertiary hypothyroidism. It is concluded that hormonal and structural changes in the thyroid gland during long-term hypopinealism should be regarded as an experimental model of hypothyroidism of neuroendocrine origin.
It has been shown that gestational stress of mothers leads to the birth of offspring with decreased body weight and a low level of leptin in the plasma. In adulthood in these offspring with the same amount of consumed food weight and fat mass higher than the corresponding figures in the offspring of mothers intact. The sons of stressed mothers established the presence of leptin resistance hypothalamic structures regulate the body’s energy, which is manifested in the absence of anorectic’s effects at hyperleptinemia. Long-term intake of fructose in the body the children of stressed mothers leads to aggravation due to leptin resistance and gestational already at a young age can contribute to the development of obesity.
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