Sexual desire have been associated with a decline in sexual desire. Though it is not used as medication, the drug methamphetamine has a strong positive effect on many aspects of sexual behaviour, including sexual desire. Sexual desire is said to be influenced by androgens in men and by androgens and estrogens in women. Many studies associate the sex hormone, testosterone with sexual desire. Testosterone is mainly synthesized in the testes in men and in the ovaries in women. Another hormone thought to influence sexual desire is oxytocin. Exogenous administration of moderate amounts of oxytocin has been found to stimulate females to desire
Melanocyte-stimulating hormone when the animal is in a dark location. This causes pigment to be dispersed in pigment cells in the toad's skin, making it become darker, and harder for predators to spot. The pigment cells are called melanophores and therefore, in amphibians, the hormone is often called melanophore-stimulating hormone. An increase in MSH will cause darker skin in humans too. MSH increases in humans during pregnancy. This, along with increased estrogens, causes increased pigmentation in pregnant women. Cushing's disease due to excess adrenocorticotropic hormone (ACTH) may also result in hyperpigmentation, such as acanthosis nigricans in the axilla. Most people with primary