Anorexia nervosa

• Onset typically before the age of 25 years
• One of the most important causes of secondary amenorrhoea in adolescents
• Amenorrhoea frequently pre-dates weight loss

• Weight loss >25% original body weight
• Distorted body image with implacable attitude towards eating

• Exclude medical illness that could cause weight loss
• Exclude other psychiatric disorders

• Associated with lanugo hair, bradycardia , hypotension, constipation, hypothermia, vomiting (may be self-induced) and periods of over-activity

• Psychiatric referral required  

• May occur in adolescents and present with primary amenorrhoea

• FSH and LH levels are low and may be undetectable

• Oestradiol and progesterone low. Progesterone challenge test typically negative

• Cortisol elevated

• Prolactin normal

• TSH and T4 levels are normal but T3 and reverse T3 are elevated

• Changes revert to normal with weight gain but 30% remain amenorrhoeic

• Response to GnRH is regained at ~15% below the ideal body weight and occurs before the resumption of menses