The thyroid gland is an organ in the front of the neck that controls energy metabolism, gene transcription and growth, and development by creating and releasing two hormones known as T3 and T4. All the cells in your body are likely targets of these hormones. In some circumstances, the function of the thyroid gland is related to the secretion of leptin by the fat tissue. This relationship is still open to exploration by researchers.
FUNCTION OF LEPTIN
Leptin is an important hormone that regulates body weight and the caloric intake in your diet. It's best known for promoting a feeling of satiety and fullness after meals. Leptin provides the key link between the energy you need and the energy you consume. A fall in leptin levels, on the other hand, acts to increase appetite, decrease energy expenditure and favor a state of survival due to a paucity in calories.
LEPTIN AND THE THYROID
The human body has a complex set of feedback mechanisms that regulate the intake and metabolism of energy. Evidence suggests that leptin targets cells that release a hormone known as TRH, which in turn stimulates the release of a thyroid-stimulating hormone, or TSH for short. TSH is the hormone that regulates the production and release of T3 and T4 in the thyroid gland. What this means is that leptin appears to have an indirect effect on thyroid function, although this relationship is still not completely understood.
THYROID FUNCTION
In animal models, leptin and the thyroid gland seem to work together to facilitate a transition from the fed to the starved state or in response to severe illness. The T3 and T4 hormones are involved in the starvation-induced decrease in the production of heat within the human body --- a process known as thermogenesis. This in turn may influence the rate of caloric expenditure. Both rodent and human studies of leptin in the blood, however, have not shown a consistent relationship between thyroid function and the concentration of leptin.
LEPTIN DEFICIENCY
A state of leptin deficiency has been known to significantly alter the daily circadian rhythm of TRH release. Some research has posited that this may cause hypothyroidism, a condition in which the thyroid gland fails to produce the necessary amount of T3 and T4. A paper published in the journal "Thyroid Research" suggests, however, that the thryroid function of leptin-deficient patients is normal. Despite its role, leptin may not be required for normal thyroid function.