Is prolactin measurement of value during inferior petrosal sinus sampling in patients with adrenocorticotropic hormone-dependent Cushing's Syndrome?

Ketogenic Diet Initially Masks Symptoms of Hypercortisolism in Cushing's Disease

Cushing’s syndrome (CS) is a diagnosis used to describe multiple causes of serum hypercortisolism. Cushing’s disease (CD), the most common endogenous subtype of CS, is characterized by hypercortisolism due to a pituitary tumor secreting adrenocorticotropic hormone (ACTH). A variety of tests are used to diagnose and differentiate between CD and CS. Hypercortisolism has been found to cause many metabolic abnormalities including hypertension, hyperlipidemia, impaired glucose tolerance, and central adiposity. Literature shows that many of the symptoms of hypercortisolism can improve with a low carb (LC) diet, which consists of consuming <30 g of total carbohydrates per day. Here, we describe the case of a patient with CD who presented with obesity, hypertension, striae and bruising, who initially improved some of his symptoms by implementing a LC diet. Ultimately, as his symptoms persisted, a diagnosis of CD was made. It is imperative that practitioners realize that diseases typically associated with poor lifestyle choices, like obesity and hypertension, can often have alternative causes. The goal of this case report is to provide insight on the efficacy of nutrition, specifically a LC diet, on reducing metabolic derangements associated with CD. Additionally, we will discuss the importance of maintaining a high index of suspicion for CD, especially in those with resistant hypertension, obesity and pre-diabetes/diabetes.

Does concomitant prolactin measurement ıncrease the accuracy of ınferior petrosal sinus sampling?

INTRODUCTION

Prolactin (PRL) measurement during inferior petrosal sinus sampling (IPSS) can be helpful to improve the accuracy. We aimed to evaluate the effect of measuring PRL levels as a predictor for the accuracy of IPSS and evaluate its impact on the lateralization of adenomas.

METHODS

In this retrospective cohort study, we reviewed 51 patients who had undergone IPSS for the investigation of ACTH-dependent hypercortisolism.

RESULTS

Forty-nine patients had proven Cushing's disease (CD), one had EAS, and the remaining one patient had adrenal adenoma. Forty-seven patients had an above 2 ACTH IPS/P ratio at baseline, and all the post-corticotropin-releasing hormone (CRH) ACTH IPS/P ratios of patients with proven CD were above 3. In these two patients whose ACTH IPS/P ratio at baseline was below 2, PRL IPS/P ratios were above 1.8 in only the dominant side, which was considered secondary to a prolactin intersinus gradient due to the biological effects of the tumor. PRL-adjusted ACTH IPS/P ratios were > 1.3 in all patients with proven CD; it was 0.7 in the patient with EAS. Surgically confirmed positive lateralization was observed in 55.1% of patients with the ACTH gradient, but when PRL-adjusted ACTH IPS/IPS ratios were used in addition to the ACTH gradient, the ratio increased to 67.3%.

CONCLUSION

Although PRL-adjusted ACTH IPS/P ratios can be helpful to improve the accuracy of results during IPSS procedures, a prolactin intersinus gradient towards the ACTH-dominant side in patients with CD may invalidate PRL as an indicator of pituitary venous outflow.

Inferior petrosal sinus sampling in Cushing's syndrome: usefulness and pitfalls

In patients with ACTH-dependent Cushing's syndrome (CS), the differentiation between Cushing's disease (CD) and ectopic ACTH secretion (EAS) can often be challenging. The traditionally used biochemical tests have limited diagnostic accuracy and imaging modalities may fail to detect the culprit lesion. Inferior petrosal sinus sampling (IPSS) was introduced more than 3 decades ago as a test with optimal diagnostic accuracy and has since become the gold standard in the differential diagnosis between CD and EAS. However, several, albeit rare, pitfalls may limit its diagnostic accuracy and awareness is needed to avoid incorrect interventions. Moreover, it is an invasive and demanding procedure, available in a limited number of centers worldwide. This review aims to critically present the usefulness and pitfalls of IPSS and define strategies for its optimal place in the contemporary management of CS.

Cushing's Disease

In patients with Cushing's disease (CD), prompt diagnosis and treatment are essential for favorable long-term outcomes, although this remains a challenging task. The differential diagnosis of CD is still difficult in some patients, even with an organized stepwise diagnostic approach. Moreover, despite the use of high-resolution magnetic resonance imaging (MRI) combined with advanced fine sequences, some tumors remain invisible. Surgery, using various surgical approaches for safe maximum tumor removal, still remains the first-line treatment for most patients with CD. Persistent or recurrent CD after unsuccessful surgery requires further treatment, including repeat surgery, medical therapy, radiotherapy, or sometimes, bilateral adrenalectomy. These treatments have their own advantages and disadvantages. However, the most important thing is that this complex disease should be managed by a multidisciplinary team with collaborating experts. In addition, a personalized and individual-based approach is paramount to achieve high success rates while minimizing the occurrence of adverse events and improving the patients' quality of life. Finally, the recent new insights into the pathophysiology of CD at the molecular level are highly anticipated to lead to the introduction of more accurate diagnostic tests and efficacious therapies for this devastating disease in the near future.

Diagnostic utility of Gallium-68-somatostatin receptor PET/CT in ectopic ACTH-secreting tumors: a systematic literature review and single-center clinical experience

PURPOSE

Tumors causing ectopic Cushing's syndrome (ECS) are often not visible with conventional imaging. Gallium-68-DOTATATE, DOTATOC, and DOTANOC positron emission tomography/computed tomography (⁶⁸Ga-SSTR PET/CT) reportedly exhibits greater sensitivity in identifying an ECS source, however, evidence is limited to mainly case reports and a few small retrospective studies. Previous systematic ECS imaging review has shown ⁶⁸Ga-SSTR PET/CT sensitivity is similar to CT (81.8%) in histologically-proven cases and is 100% in covert-cases, however, the number of patients was small and no occult cases were reported.

METHODS

We performed a systematic literature review of ⁶⁸Ga-SSTR PET/CT use in ECS patients. We also report 6 consecutive patients with confirmed active and occult ECS who underwent ⁶⁸Ga-DOTATATE PET/CT and were followed at our institution between 2014 and 2019.

RESULTS

We identified 33 articles (23 case-reports, 4 case-series, 5 retrospective studies and 1 prospective study) detailing ⁶⁸Ga-SSTR PET/CT in 69 ECS patients. Overall ⁶⁸Ga-SSTR PET/CT sensitivity was 64.0%, while in histologically confirmed cases (67 lesions), sensitivity was 76.1%. There were two false-positives cases, both in the adrenal glands. In covert cases, ⁶⁸Ga-SSTR PET/CT identified 50% of lesions. There were ten occult cases where all imaging failed to identify an adrenocorticotropic hormone source; source remains unknown. In our case series, ⁶⁸Ga-DOTATATE PET/CT showed decreased uptake in pancreatic neuroendocrine tumor in one patient and did not help identify an ECS source in 5 patients.

CONCLUSION

Both this systematic literature review, the largest to date, and our single- center experience demonstrate a lower than previously reported ⁶⁸Ga-SSTR PET/CT sensitivity for ECS, especially in occult lesions. We suggest that the data on ⁶⁸Ga-SSTR PET/CT in ECS is subject to publication bias, and false-negatives are likely underreported; it's diagnostic value for ECS needs further study.

Prolactin-adjusted ACTH Ratio in Predicting Lateralization of ACTH Source During Simultaneous Bilateral Inferior Petrosal Sinus Sampling in Patients with Cushing's Disease

INTRODUCTION

Prolactin-adjusted adrenocorticotropic hormone (ACTH) ratio is used to improve the diagnostic accuracy of bilateral inferior petrosal sinus sampling (BIPSS) for lateralization of pituitary adenoma.

OBJECTIVE

To study the use of prolactin for successful catheterization during BIPSS, the role of prolactin-normalized ACTH ratio for confirmation of Cushing's disease (CD) and prolactin-adjusted ACTH ratio in predicting the lateralization.

PATIENTS AND METHODS

BIPSS was done in patients with CD; prolactin-adjusted ACTH ratio was compared with intersinus ACTH ratio, magnetic resonance imaging, and intraoperative findings for localization of pituitary adenoma. Histopathology was taken as "gold standard" for the diagnosis of CD.

RESULTS

Eight patients underwent BIPSS. All the patients underwent transsphenoidal surgery. All these patients had proper venous sampling during BIPSS as determined by inferior petrosal sinus (IPS):Peripheral prolactin ratio of ≥1.8. Prolactin-normalized ACTH ratio of ≥1.3 was achieved in all the eight patients, which was consistent with the diagnosis of CD. Concordance of intersinus ACTH ratio ≥1.4 with the intraoperative findings was found in five of eight (62.5%) patients depicting correct lateralization. Concordance of prolactin-adjusted ACTH ratio with intraoperative findings was found in four of eight (50%) patients. Seven of eight patients had concordance of intersinus ACTH ratio with prolactin-adjusted ACTH ratio.

CONCLUSION

Prolactin is a useful marker for successful catheterization, confirming the diagnosis of CD during BIPSS, and prolactin-adjusted ACTH ratio does not add to the accuracy of lateralization of pituitary adenoma compared with intersinus ACTH ratio.

The value of prolactin in inferior petrosal sinus sampling with desmopressin stimulation in Cushing's disease

Prolactin may reduce false-negative results in diagnosing Cushing's disease (CD) during inferior petrosal sinus sampling (IPSS). Prolactin normalization could improve the accuracy of IPSS in predicting adenoma lateralization in CD. However, none of the previous studies had involved the use of desmopressin during IPSS. Our objective was to examine the utility of prolactin measurement during IPSS with desmopressin stimulation. We conducted a retrospective analysis of 40 patients (including 31 females) with ACTH-dependent Cushing's syndrome who underwent IPSS between 2010 and 2013. Thirty-eight CD patients were partitioned into true positive (n = 35) and false negative (n = 3). The proportion of improper IPSS venous sampling defined by corresponding IPS:P (inferior petrosal sinus to peripheral) prolactin ratio <1.8 was significantly different between two groups (P = 0.004). Applying a prolactin-normalized ACTH IPS:P ratio >0.8 cutoff could increase the sensitivity of IPSS to 38/38 (100 %). Among the 31 patients with histopathologically proven adenoma localization, correct prediction of adenoma lateralization was obtained in 14/31 (45 %) patients by a peak intersinus ACTH gradient of ≥1.4 in baseline and was not improved by desmopressin stimulation. Left-right intersinus gradients of unilateral prolactin-adjusted ACTH IPS:P ratios could increase the correct prediction of adenoma lateralization to 20/31 (65 %) in baseline and 24/31 (77 %) (P = 0.006) after desmopressin stimulation, respectively. Prolactin is helpful to adjust negative results of IPSS with desmopressin stimulation. It may improve the accuracy in predicting adenoma lateralization in CD as well.