The cause of hirsutism can be either an increased level of androgens (male hormones) or an oversensitivity of hair follicles to androgens.

Polycystic ovary syndrome
Cushing's disease
Tumors in the ovaries or adrenal gland (cancer)
Certain medications
Congenital adrenal hyperplasia
Insulin resistance
Hormone imbalance
Genetics
Pregnancy
Aging
Obesity
Anorexia Nervosa

Have you taken these factors into consideration and ruled them out?

N-Acetyl-Cysteine is an altered form of the amino acidcysteine which is commonly found in food and synthesized by the body.It is used for its antioxidant properties and for for lung congestion.  As I it tends to deplete the body of zinc and other minerals, I would not recommend long term usage, and, although it has other uses, I don't see where it would help in the treatment of hirsutism.  Also, the fact that it is an "altered" form of anything raises red flags with me.

Treatments for hursutism are:

Black cohosh 
Goats rue 
Fenugreek 
Chaste tree  
Licorice, although licorice should not be taken daily for prolonged periods without breaks since it can cause low potassium levels.
Exercise and weight loss could be very beneficial.
Spearmint tea.

IMPORTANT NOTE:  Chronic licorice use may lead to loss of potassium and high blood pressure.

Hope this helps. Let me know which route you use and how you do.

Hugs,

Luella

Though Luella is quite right in warning about N-acetyl cysteine, generally speaking I rather like it – so long as one heeds the warnings at the end of this post.

N-acetyl cysteine is an amino acid that serves as a precursor for the synthesis of glutathione, a detoxifying agent in the body. N-acetyl cysteine does not occur in foods. Its precursor, L-cysteine, also called just “cysteine”, occurs in most high-protein foods.  NAC also functions as an antioxidant that has been used to combat viruses. It may also help the liver detoxify a wide range of pollutants such as cigarette smoke, auto exhaust, certain herbicides, and some toxic metals.

Cysteine is a non-essential amino acid that can be manufactured in the liver. It is obtained in the diet from beans, brewer’s yeast, broccoli, Brussels sprouts, dairy products, eggs, fish, garlic, legumes, meat, nuts, onions, red peppers, seafood, seeds, soy, whey, and whole grains. N-acetyl cysteine (NAC) is a modified form of cysteine.

NAC may also reduce the viscous mucous associated with respiratory diseases like chronic bronchitis. It is also used as an antidote for acetaminophen poisoning.

Used for anti-aging, cysteine may help to diminish the effects of aging, protect against heart disease and cancer, boost the immune system, promotes metabolism of fats and production of muscle tissue, aid healing after surgery, promote hair growth, and prevent hair loss. It is also known to work synergistically with vitamin E and selenium as an antioxidant, protecting against the damaging effects of radiation, acetaldehyde, acrolein in tobacco smoke, alcohol and environmental pollutants.

Several studies have found that NAC is beneficial to patients with chronic bronchitis and angina; there is also preliminary evidence to suggest that it may help to prevent colon cancer Some experts believe that NAC increases the efficacy of chemotherapy drugs and helps to alleviate their side effects. Very high doses of NAC are given to patients in hospital to treat acetaminophen poisoning.

Symptoms of cysteine deficiency include: apathy, loss of pigmentation in hair, edema, lethargy, liver damage, muscle loss, skin lesions, weakness, fat loss, and slowed growth in children.

Optimal levels of NAC and cysteine have not been determined. 250 to 1,500 mg of NAC per day has been used in clinical studies with no adverse effects.

The maximum safe levels for cysteine have not been established -there are no known signs of toxicity from cysteine. NAC appears to be a very safe supplement even in high doses, however an animal study found that 60-100 times the normal dose could cause liver injury. Note: NAC is known to have antioxidant activity, however one study found that daily doses of 1.2g or more increased oxidative stress.

SIDE EFFECTS/CONTRAINDICATIONS:

• The most common side effect is nausea and vomiting (in one study 19% of the participants reported vomiting).
  
• People with diabetes mellitus and allergies to eggs, milk, or wheat should not take supplementary cysteine.
  
• People taking the drug nitroglycerin may experience severe headaches when taking NAC.
• Cysteine supplements must be taken with vitamin C to prevent cysteine being converted to cystine, which may form kidney or bladder stones.
• People with kidney or liver disease should consult their doctor before taking supplementary cysteine.
• Long term use may lead to mineral depletion and thus should be accompanied with a good overall mineral supplementation program for both major and trace minerals (especially zinc and copper).