Exploring a Causal Connection between Acromegaly and Schizophrenia

Although the first clinical case associating acromegaly with schizophrenia was reported more than 60 years ago, researchers continue to ponder the association between the 2 disorders.

Schizophrenia is well-known for its hallucinations or delusions, disorganized speech, flat affect, and impaired cognitive function, and its prevalence is 4,500-5,000 patients per million with an annual incidence rate of 11—15 per 100,000 person-years. The less prevalent condition known as acromegaly results from excessive growth hormone (GH) secretion that leads to elevated insulin-like growth factor-1 (IGF-1) as the liver responds to GH.

A study published in the March 2014 issue of Schizophrenia Bulletin identified 3 patients with comorbid schizophrenia and acromegaly in the Madrid, Spain, area, which is home to approximately 6.5 million people. Based on statistical analysis, the researchers concluded the 3 patients represent an observed prevalence 10 times higher than expected, which suggested a possible causal connection between acromegaly and schizophrenia.

The study’s results indicated each patient received a different long-term dopamine antagonist prior to acromegaly diagnosis: Patient 1 had received paliperidone 12 mg/day and amisulpride 400 mg/day; Patient 2 had taken clozapine 600 mg/day; and Patient 3 had received haloperidol 10 mg/day. Two patients underwent transsphenoidal surgery, which resulted in a mixed GH- and prolactin-secreting adenoma in one patient and a pure GH-secreting adenoma in the other.

The study discussed several potential pathophysiologic mechanisms as possible links, including alterations in dopaminergic neurotransmission due to schizophrenia and the pharmacologic blockage of dopamine receptors during treatment that may cause acromegaly.

The case reports added an additional layer of evidence of a causal relationship between acromegaly and schizophrenia. However, the low prevalence of both disorders, especially acromegaly, makes it a challenging topic for further research.