Macroprolactinoma with secondary resistance to dopamine agonists: a case report and review of the literature

BACKGROUND

Resistance to dopamine agonists is not uncommonly seen in prolactinomas. However, development of resistance to dopamine agonists after an initial period of robust treatment response is rare, and only 39 cases have been reported in the past four decades. We describe a Chinese man with this rare condition and explored the postulated mechanisms that may explain this phenomenon. We compiled similar cases that were previously reported and compared their etiology, progress, and response to treatment. On the basis of these cases, we derived a list of differential diagnoses to consider in patients with secondary resistance to dopamine agonists.

CASE PRESENTATION

A 63-year-old Chinese man presented with blurred vision and was subsequently diagnosed with a macroprolactinoma. He had initial response to cabergoline but developed secondary resistance to it after 5 years. The prolactinoma continued to grow, and his serum prolactin remained markedly elevated despite adherence to escalating dosages of cabergoline up to 6 mg/week. The patient finally underwent transsphenoidal surgery and was found to have a sparsely granulated lactotroph tumor with Ki-67 index of 5%. Postoperatively, there was improvement in his serum prolactin level, although he still required treatment with cabergoline at 6 mg/week.

CONCLUSIONS

Surgery can facilitate disease control in patients with prolactinomas that develop secondary resistance to dopamine agonists. Malignant prolactinoma is an important differential diagnosis in this group of patients, especially when serum prolactin remains markedly elevated despite resolution or stability of the primary pituitary lesion, suggesting a metastatic source of prolactin secretion.

Myxedema Coma Precipitated by Iohexol: Case Report and Brief Literature Review on the Wolff-Chaikoff Effect

Background: Failure to escape from the Wolff-Chaikoff effect (WCE) causes hypothyroidism. Methods: This is the first report of myxedema coma after iohexol administration. The failure of the escape phenomenon in this patient was longer than existing reports. Results: The patient received 42,000 mg of iodine in iohexol cumulatively and developed myxedema coma after 16 days. She was subsequently found to have pre-existing primary hypothyroidism that was treated with levothyroxine 50 μg daily, but had defaulted treatment. She was discharged with levothyroxine 100 μg daily and this was weaned to 50 μg daily over 12 months. Conclusions: Iodine-based contrast media (ICM) can aggravate primary hypothyroidism. In severe cases, it may precipitate myxedema coma. Patients with thyroid disorders should be informed to monitor for aggravation of their symptoms after ICM administration. Long-term follow-up of thyroid function may be needed in patients who fail to escape from the WCE.

Efficacy and safety of anticoagulation in thyrotoxic atrial fibrillation: a systematic review and meta-analysis

Background

Evidence on the efficacy and safety of anticoagulation in preventing stroke and thromboembolic events in people with thyrotoxic atrial fibrillation is scarce.

Objective

We evaluated the efficacy and safety of anticoagulation in people with thyrotoxic atrial fibrillation.

Methods

Our study protocol was published in the International Prospective Register of Systematic Reviews (registration no. CRD42020222782). Four databases and two systematic review registers were searched through 25 November 2020 for interventional and observational studies comparing anticoagulation therapy with active comparators, placebo, or no treatment in people with thyrotoxic atrial fibrillation. Random-effects meta-analysis and sensitivity analysis were performed. Quality of evidence was described using the GRADE framework.

Results

In the study, 23,145 records were retrieved. One randomized controlled trial and eight cohort studies were ultimately included. Effect estimates on the efficacy and safety of anticoagulation were extracted. Meta-analysis using the inverse variance and random-effects methods was conducted on four cohort studies with 3443 participants and 277 events. Anticoagulation in people with thyrotoxic atrial fibrillation reduced the risk of ischemic stroke and systemic thromboembolism by 3% (95% CI: 1-6%). Warfarin may prevent ischemic stroke in people with thyrotoxic atrial fibrillation if the CHA2DS2-VASc score exceeds 1 and when atrial fibrillation persists beyond 7 days. Direct oral anticoagulants may be associated with fewer bleeding events than warfarin.

Conclusions

Anticoagulation prevents ischemic stroke and systemic thromboembolism in people with thyrotoxic atrial fibrillation. Direct oral anticoagulants may be associated with fewer bleeding events.

Dexamethasone suppression test versus selective ovarian and adrenal vein catheterization in identifying virilizing tumors in postmenopausal hyperandrogenism - a systematic review and meta-analysis

OBJECTIVE

The diagnostic accuracy of tests in identifying virilizing tumors in postmenopausal hyperandrogenism is limited. This systematic review compares the dexamethasone suppression test against selective ovarian and adrenal vein sampling of androgens in distinguishing neoplastic from non-neoplastic causes of postmenopausal hyperandrogenism.

METHODS

Diagnostic test accuracy studies on these index tests in postmenopausal women were selected based on pre-established criteria. The true positive, false positive, false negative, and true negative values were extracted and meta-analysis was conducted using the hierarchical summary receiver operator characteristics curve method.

RESULTS

The summary sensitivity of the dexamethasone suppression test is 100% (95% CI 0-100%) and that for selective venous sampling is 100% (95% CI 0-100%). The summary specificity of the dexamethasone suppression test is 89.2% (95% CI 85.3-92.2%) and that for selective venous sampling is 100% (95% CI 0.3-100%).

CONCLUSION

There is limited evidence for the use of dexamethasone suppression test or selective venous sampling in identifying virilizing tumors in postmenopausal hyperandrogenism.

Gonadotropin-Releasing Hormone Analogue Stimulation Test Versus Venous Sampling in Postmenopausal Hyperandrogenism

Postmenopausal hyperandrogenism can be due to excessive androgen secretion from adrenal or ovarian virilizing tumors or nonneoplastic conditions. The etiology of postmenopausal hyperandrogenism can be difficult to discern because of limited accuracy of current diagnostic tests. This systematic review compares the diagnostic accuracy of the gonadotropin-releasing hormone (GnRH) analogue stimulation test against selective ovarian and adrenal vein sampling of androgens in distinguishing neoplastic from nonneoplastic causes of postmenopausal hyperandrogenism. Diagnostic test accuracy studies on these index tests in postmenopausal women were selected based on preestablished criteria. The true positive, false positive, false negative, and true negative values were extracted and meta-analysis was conducted using the hierarchical summary receiver operator characteristics curve method. The summary sensitivity of the GnRH analogue stimulation test is 10% (95% confidence interval [CI], 1.1%-46.7%) and that for selective venous sampling is 100% (95% CI, 0%-100%). Both tests have 100% specificity. There is limited evidence for the use of either test in identifying virilizing tumors in postmenopausal hyperandrogenism.