Endocrine Abstracts

Introduction

Maturity Onset Diabetes of the Young (MODY) is an autosomal dominant disease, diagnosed mainly in young individuals with a strong family history of diabetes, that results from mutations impairing pancreatic β cell function. The MODY 3 subtype, caused by a HNF1α mutation, with consequent deficit in insulin secretion, is the most frequent and responds more effectively to sulfonylureas, compared to metformin. Acromegaly is a rare condition characterized by hypersecretion of growth hormone, usually by a pituitary adenoma, that leads to multiple comorbidities, including insulin resistance. There is no association described in the literature between MODY 3 and acromegaly.

Case report

A 33-year-old man, with obesity, obstructive sleep apnea and colon polyposis, with family history of MODY 3, came to an endocrinology appointment after being diagnosed with diabetes 3 years before. He was on insulin therapy since diagnosis, with negative pancreatic β cell immunity. At the first visit we noticed an acromegalic facies, a BMI of 31.8 kg/m², with a suggestive history of acromegaly for about 10 years. In this context, a pituitary study was requested that revealed hGH 5.04 ng/ml (N 0.06–5.00), IGF-1 773 ng/ml (N 71.2–234), ACTH 64.0 pg/ml (N 9–52), cortisol 14.2 µg/dl (N 6.2–19.4) and prolactin 404.0 ng/ml (N 4.04–15.2). At that time, he was on insulin glargine 10 units, gliclazide 60 mg/day and metformin 2000 mg/day, with a HbA1C of 7.4%. MRI revealed a pituitary macroadenoma with deviation of the pituitary stalk. Therefore, the diagnosis of acromegaly was assumed and the patient was started on bromocriptine 10 mg/day. Insulin was suspended and gliclazide increased to 90 mg/day. In the following months, he noticed a great improvement in glycemic control, leading to self-suspension of gliclazide. Six months after, metformin had been reduced to 1000 mg/day, with a HbA1c of 6.1% and a marked decrease in IGF-1 values (279 ng/ml), with normalization of prolactin levels. One year after diagnosis the patient is still kept on bromocriptine 10 mg/day and metformin 1000 mg/day, with HbA1c of 5.7%, and with a positive genetic study for MODY 3. Considering the favorable evolution, surgical treatment was postponed.

Conclusion

It is a rare case of association of MODY 3 and acromegaly. Bromocriptine therapy allowed a clear improvement of tumor secretion and glycemic control, highlighting the role of insulin resistance in the presented case.