Endocrine Abstracts

Introduction: Hyperprolactinaemia may be associated with weight gain and obesity, suggesting that prolactin may modulate body composition and weight. Treatment that normalises prolactin levels using dopamine agonists frequently leads to weight loss and provides further evidence for the association.

Case: A 28-year-old South Asian male with a body mass index of 27.2 kg/m² was referred to a weight management clinic with a five year history of weight gain despite regularly attending the gym for 2 h 4–5 days per week. He had frequently been seen by his GP who had consistently given lifestyle and dietary advice despite his regular attendance at the gym with no improvement. He also complained of short-term memory loss, feeling tired and lethargic for several years. He was not diabetic and blood pressure and cholesterol were normal. Examination findings were unremarkable. Prolactin level was 6251 mU/l (86–324) testosterone was 8.8 nmol/l (8.6–35.0) and his TSH was 1.5 mU/l (0.3–4.6).

An MRI scan showed a 9×9 mm bulge arising from the pituitary gland consistent with a microprolactinoma. He was commenced on carbergoline 250 μg twice weekly and his prolactin level 3 months later had improved considerably to 443 mU/l and testosterone had showed some improvement at 9.8 nmol/l. His weight went from 85 to 86.2 kg but measurement of bioimpedance showed that his fat% went down from 29.1 to 26.8%, and fat free mass went up from 60 to 63 kg, suggesting a loss of fat and gain in muscle mass.

Discussion: Although it is widely accepted that dietary intake and lifestyle factors are the major contributors to weight gain and subsequent obesity, weight gain is associated with a number of endocrine disorders including hyperprolactinaemia, and should be considered as a differential diagnosis for endocrine obesity when changing lifestyle factors has not affected weight.