Clinical and hormonal findings in patients presenting with high IGF-1 and growth hormone suppression after oral glucose load: a retrospective cohort study

"Micromegaly": Acromegaly with apparently normal GH, an entity on its own?

A small proportion of the patients with acromegaly present with apparently normal basal GH levels and suppressible GH levels despite increased IGF-1 levels, a pattern called micromegaly by some authors. Whether this pattern represents a distinct entity or is just an expression of acromegaly in its early stages is still a matter of debate. Nevertheless, these patients have some peculiar characteristics such as being more likely older and male, mostly harbour microadenomas or small macroadenomas, and have lower IGF-1 and postglucose GH levels. Even though, the frequency and severity of clinical signs and comorbidities are similar to those of patients with classic acromegaly. In conclusion, micromegaly seems to be a distinct clinical entity with a different biological behavior characterized by a low GH output.

Acromegaly among a Moroccan population

Acromegaly is defined as an acquired dysmorphytic syndrome due to excessive secretion of growth hormone (GH) and consequently of insulin-like growth factor-1 (IGF-1). This is a retrospective study of patients who were hospitalized in the Endocrinology Department of the Mohammed V Military Academic Hospital in Rabat over a period of 14 years (2008 to 2022), reporting on their clinical, paraclinical and evolutionary profiles and comparing the results with the data in the literature. Nineteen patients were included in our study. The mean age was 42.7 ± 11.6 years, with a male predominance. The clinical manifestations were dominated by a dysmorphic syndrome present in 97.4% of cases, followed by complications related to acromegaly in 88.9% of cases. The diagnosis was made when GH and IGF-1 values were elevated in 88.9% and 93.8% of cases, respectively; with a mean GH value of 25.1 μg/L. Magnetic resonance imaging (MRI) was used to diagnose the location of pituitary adenoma in all cases, 78.9% of which were macroadenomas and 21.1% microadenomas. The majority of patients (78.9%) had recourse to transsphenoidal surgery. Medical treatment was carried out in 89.5% of cases. Postoperative radiotherapy was performed in 33% of cases. Disease control was achieved in 30.1% of cases. This study shows the complex management of acromegaly. Disease control is a necessary condition in order to avoid complications, but is often difficult to obtain.

[Acromegaly screening in patients with hyperprolactinemia and pituitary adenoma]

BACKGROUND

Hyperprolactinemia accompanies growth hormone hypersecretion in approximately 25-39% of cases. There is a recommendation to determine the level of prolactin in clinical guidelines for diagnosis and treatment of acromegaly. However, there is no understanding of the necessity to investigate the IGF-1 level in patients with hyperprolactinemia and a pituitary adenoma.

AIM

Determining the proportion of patients with hyperprolactinemia and pituitary adenoma, who were examined for IGF-1 levels, and identifying the proportion of patients with acromegaly among this cohort.

MATERIALS AND METHODS

Between December 2019 and December 2022 a single-center observational single-stage single-sample uncontrolled study was conducted. At the first stage of the study, the proportion of patients with pituitary adenoma and hyperprolactinemia with studied IGF-1 levels was determined, according to medical records. At the second stage of the study, patients without known indicators of IGF-1 were determined. The concentration of growth hormone was studied during the oral glucose load in the case of increased IGF-1 levels.

RESULTS

At the first stage, 105 patients were included in the study. The level of IGF-1 was determined in 41/105 (39%) cases. There were 22/41 (53.7%) cases in the subgroup with pituitary incidentalomas and 19/64 (29.7%) cases in the subgroup with hyperprolactinemia among them. At the second stage, the IGF-1 level was additionally determined in 53 patients with hyperprolactinemia and pituitary adenoma (total 94 patients). The level of IGF-1 was elevated in 11/94 patients, further acromegaly was confirmed in 3/94 patients (3.2%).

CONCLUSION

In real clinical practice the level of IGF-1 is studied only in 39% of cases in patients with pituitary adenoma and hyperprolactinemia. The disease was detected in 3 cases (3.2%) out of 94 people with hyperprolactinemia and pituitary adenoma without clinical manifestations of acromegaly. We consider the study of IGF-1 levels justified as a screening for acromegaly in patients with hyperprolactinemia and pituitary adenoma.

Biochemical discrepancies in the evaluation of the somatotroph axis: Elevated GH or IGF-1 levels do not always diagnose acromegaly

The most frequent diagnosis underlying the finding of an elevated growth hormone (GH) and insulin-like growth factor-1 (IGF-1) is acromegaly due to a GH-secreting pituitary tumour. However, GH and IGF-1 levels can be discordant in patients with acromegaly due to early or partially treated disease, or there might be another cause of high GH or high IGF-1 unrelated to acromegaly, such as pre-analytical and technical pitfalls, physiological circumstances and pathological conditions. High GH and normal or low serum IGF-1, or alternatively, normal GH with elevated serum IGF-1, should be carefully assessed to avoid misinterpreting the activity of acromegaly or misdiagnosing a patient with acromegaly. We summarise here these biochemical discrepancies in the evaluation of the somatotroph axis.

The biochemical diagnosis of acromegaly: revising the role of measurement of IGF-I and GH after glucose load in 5 questions

INTRODUCTION

Acromegaly is a rare disorder characterized by the excessive secretion of growth hormone (GH), mostly caused by pituitary adenomas. While in full-blown cases the diagnosis is easy to establish, milder cases are more challenging. Additionally, establishing whether full cure after surgery is reached may be difficult.

AREAS COVERED

In this article, we will review the challenges posed by the variability in measurements of GH and its main effector insulin-like growth factor I (IGF-I) due to both biological changes, co-morbidities, and assays variability.

EXPERT OPINION

Interpretation of GH and IGF-I assays is important in establishing an early diagnosis of acromegaly, in avoiding misdiagnosis, and in establishing if cure is achieved by surgery. Physicians should be familiar with the variables that affect measurements of these 2 hormones, and with the performance of the assays available in their practice.

Characteristics and treatment outcomes of micromegaly - acromegaly with apparently normal basal GH: A retrospective study and literature review

Objective. Micromegaly describes a subgroup of patients with clinically evident acromegaly and elevated insulin-like growth factor I (IGF-I) with apparently normal basal growth hormone (bGH) and often a glucose-suppressed growth hormone (GH) of <1 ng/mL at diagnosis. It is controversial whether this condition is a distinct clinical entity or a classic acromegaly in early stages. The aim of the present article was to characterize the prevalence, clinical and biochemical characteristics, and therapeutic outcomes of micromegaly. Methods. A retrospective study of patients with an acromegaly followed ≥1 year at a tertiary center from 1995 to 2019. Patients without IGF-I or GH measurements at diagnosis were excluded. At diagnosis, bGH was considered normal if <2 ng/mL. Results. From 74 patients with acromegaly, 6 (8.1%) had normal bGH levels. There was no difference in the gender distribution, median diagnostic delay, and follow-up time between patients with normal bGH and elevated bGH. Patients with normal bGH were significantly older at time of the first acromegalic manifestation and diagnosis they had significantly lower nadir post-glucose GH and IGF-I levels, and tended to have a higher prevalence of obesity than patients with the elevated bGH. The frequency of acromegalic symptoms, signs, and other comorbidities than obesity was similar between groups. Five patients (83.3%) with normal bGH presented microadenomas. Post-operative remission and outcomes at last visit were comparable between patients with or without normal bGH. Conclusions. Normal bGH acromegaly is relatively uncommon in our patients. These patients showed differentiating characteristics from the classical acromegaly with elevated bGH. Further studies are needed to extend the knowledge about its clinical behavior, therapeutic outcomes, morbidity, and mortality.