"Marijuana and its active component THC affect multiple endocrine systems. A suppressive effect is seen on the reproductive hormones, prolactin, growth hormone, and the thyroid axis, while the HPA axis is activated. These effects are mediated through CB1 receptor activation in the hypothalamus, which directly or indirectly modulates anterior pituary function. Many of the responses observed, however, are lost with chronic administration, which is likely due to the development of tolerance. Studies in humans have had inconsistent results that may reflect differences in study design, the hormonal milieu (eg., stage in menstrual cycle) or the development of tolerance. Long-term effects on the various endocrine systems have not been clearly demonstrated, and clinical consequences, if present, are likely to be subtle."