We covered a lot of ground, and I dumped a ton of information on you. I can’t fault you for feeling a bit confused—I certainly was as I was researching this chapter. So let’s pull all the main points into a neat summary:

• Acne is linked to two groups of hormones: (1) androgens (DHEAS, testosterone, and DHT), and (2) growth hormone, insulin, and IGF-1.
• Both androgens and IGF-1 are required for the development of acne. People with dysfunctional androgen receptors produce no sebum and have no acne. Similarly, people with IGF-1 deficiency have markedly low rates of acne.
• Injecting either androgens or IGF-1 into the body has been shown to cause increased sebum production and acne.
• Both groups of hormones can stimulate sebum production and cell growth in the skin. Androgens can also stimulate keratin production and contribute to hyperkeratinization. The sebum and skin cell enhancing effects of these two groups of hormones is additive. Exposing cells to both groups of hormones stimulates them more than either group alone. Within the androgen group, DHT is the most potent stimulator, being 5 to 10 times more potent than testosterone, whereas growth hormone is by far the strongest stimulator in the other group, followed by IGF-1.
• Some acne patients may have higher than normal androgen levels, but we can’t say this of all acne patients. Many acne patients have perfectly normal androgen levels.
• Due to genetics, acne-prone skin is excessively sensitive to androgen hormones, and a little bit goes a long way for acne patients.
• The skin has all the necessary enzymes for converting the various testosterone precursor hormones to testosterone and further to DHT. The conversion of testosterone to DHT is done by the enzyme 5-alpha reductase, and there’s some evidence to believe this enzyme is overtly active in acne-prone skin.
• Insulin and IGF-1 act as booster hormones to androgens. They can stimulate androgen release from the adrenals, and increase the sensitivity of the skin to androgens.
• While there’s not much you can do to affect IGF-1 and androgen levels directly, you have a great deal of control over insulin levels.
• High insulin levels stimulate IGF-1 production in the liver. Furthermore, they suppress the production of IGF-binding proteins and increase the amount of bioactive IGF-1 in the blood.
• Finally, a subgroup of acne patients suffers from insulin resistance, but it’s difficult to say how widespread insulin resistance is among acne patients.

If I were to condense everything in this chapter into a simple action step, it would be: ‘control your insulin‘.