Nervous system Jnk1 deficiency caused increased expression of thyrotropin releasing hormone (TRH) in the hypothalamus, thyroid stimulating hormone (TSH) by the pituitary gland, and increased circulating levels of thyroid hormones (T3 and T4) in the blood. Thus hypothalamic–pituitary–thyroid axis is a crucial target of JNK1 that controls obesity. Here, TG is linked to obesity due to melanocortin 4 receptor deficiency.