BACKGROUND: Pituitary pars intermedia dysfunction (PPID) is a prevalent, age-related chronic disorder in equids. Diagnosis of PPID can be challenging because of its broad spectrum of clinical presentations and disparate published diagnostic criteria, and there are limited available treatment options.
OBJECTIVE: To develop evidence-based primary care guidelines for the diagnosis and treatment of equine PPID based on the available literature.
METHODS: Evidence-based clinical guideline using the Grading of Recommendations, Assessment, Development and Evaluation (GRADE) framework.
METHODS: Research questions were proposed by a panel of veterinarians and developed into PICO or another structured format. VetSRev and Veterinary Evidence were searched for evidence summaries, and systematic searches of the NCBI PubMed and CAB Direct databases were conducted using keyword searches in July 2022 and updated in January 2023. The evidence was evaluated using the GRADE framework.
CONCLUSIONS: The research questions were categorised into four areas: (A) Case selection for diagnostic testing, pre-test probability and diagnostic test accuracy, (B) interpretation of test results, (C) pharmacological treatments and other treatment/management options and (D) monitoring treated cases. Relevant veterinary publications were identified and assessed using the GRADE criteria. The results were developed into recommendations: (A) Case selection for diagnostic testing and diagnostic test accuracy: (i) The prevalence of PPID in equids aged ≥15 years is between 21% and 27%; (ii) hypertrichosis or delayed/incomplete hair coat shedding provides a high index of clinical suspicion for PPID; (iii) the combination of clinical signs and age informs the index of clinical suspicion prior to diagnostic testing; (iv) estimated pre-test probability of PPID should be considered in interpretation of diagnostic test results; (v) pre-test probability of PPID is low in equids aged <10 years; (vi) both pre-test probability of disease and season of testing have strong influence on the ability to diagnose PPID using basal adrenocorticotropic hormone (ACTH) or ACTH after thyrotropin-releasing hormone (TRH) stimulation. The overall diagnostic accuracy of basal ACTH concentrations for diagnosing PPID ranged between 88% and 92% in the autumn and 70% and 86% in the non-autumn, depending on the pre-test probability. Based on a single study, the overall diagnostic accuracy of ACTH concentrations in response to TRH after 30 minutes for diagnosing PPID ranged between 92% and 98% in the autumn and 90% and 94% in the non-autumn, depending on the pre-test probability. Thus, it should be remembered that the risk of a false positive result increases in situations where there is a low pre-test probability, which could mean that treatment is initiated for PPID without checking for a more likely alternative diagnosis. This could compromise horse welfare due to the commencement of lifelong therapy and/or failing to identify and treat an alternative potentially life-threatening condition. (B) Interpretation of diagnostic tests: (i) There is a significant effect of breed on plasma ACTH concentration, particularly in the autumn with markedly higher ACTH concentrations in some but not all \'thrifty\' breeds; (ii) basal and/or post-TRH ACTH concentrations may also be affected by latitude/location, diet/feeding, coat colour, critical illness and trailer transport; (iii) mild pain is unlikely to have a large effect on basal ACTH, but caution may be required for more severe pain; (iv) determining diagnostic thresholds that allow for all possible contributory factors is not practical; therefore, the use of equivocal ranges is supported; (v) dynamic insulin testing and TRH stimulation testing may be combined, but TRH stimulation testing should not immediately follow an oral sugar test; (vi) equids with PPID and hyperinsulinaemia appear to be at higher risk of laminitis, but ACTH is not an independent predictor of laminitis risk. (C) Pharmacologic treatments and other treatment/management options: (i) Pergolide improves most clinical signs associated with PPID in the majority of affected animals; (ii) Pergolide treatment lowers basal ACTH concentrations and improves the ACTH response to TRH in many animals, but measures of insulin dysregulation (ID) are not altered in most cases; (iii) chasteberry has no effect on ACTH concentrations and there is no benefit to adding chasteberry to pergolide therapy; (iv) combination of cyproheptadine with pergolide is not superior to pergolide alone; (v) there is no evidence that pergolide has adverse cardiac effects in horses; (vi) Pergolide does not affect insulin sensitivity. (D) Monitoring pergolide-treated cases: (i) Hormone assays provide a crude indication of pituitary control in response to pergolide therapy, however it is unknown whether monitoring of ACTH concentrations and titrating of pergolide doses accordingly is associated with improved endocrinological or clinical outcome; (ii) it is unknown whether monitoring the ACTH response to TRH or clinical signs is associated with an improved outcome; (iii) there is very weak evidence to suggest that increasing pergolide dose in autumn months may be beneficial; (iv) there is little advantage in waiting for more than a month to perform follow-up endocrine testing following initiation of pergolide therapy; there may be merit in performing repeat tests sooner; (v) timing of sampling in relation to pergolide dosing does not confound measurement of ACTH concentration; (vi) there is no evidence that making changes after interpretation of ACTH concentrations measured at certain times of the year is associated with improved outcomes; (vii) evidence is very limited, however, compliance with PPID treatment appears to be poor and it is unclear whether this influences clinical outcome; (viii) evidence is very limited, but horses with clinical signs of PPID are likely to shed more nematode eggs than horses without clinical signs of PPID; it is unclear whether this results in an increased risk of parasitic disease or whether there is a need for more frequent assessment of faecal worm egg counts.
CONCLUSIONS: Limited relevant publications in the veterinary scientific literature.
CONCLUSIONS: These findings should be used to inform decision-making in equine primary care practice.

BACKGROUND: Compared with levodopa, dopamine agonists (DAs) as initial treatment are associated with lower incidences of motor complications in early Parkinson\'s disease (PD). There is no strong evidence that a given DA is more potent in lower incidences of motor complications than another.
OBJECTIVE: We performed a network meta-analysis of levodopa versus DAs as monotherapy in early PD to access the risk of motor complications.
METHODS: Databases were searched up to June 2022 for eligible RCTs. Levodopa and four DAs (pramipexole, ropinirole, bromocriptine and pergolide) were investigated. The incidences of motor complications and efficacy, tolerability and safety outcomes were analyzed.
RESULTS: Nine RCTs (2112 patients) were included in the current study. The surface under the cumulative ranking curve (SUCRA) indicated that levodopa ranked first in the incidence of dyskinesia (0.988), followed by pergolide, pramipexole, ropinirole, and bromocriptine (0.704, 0.408, 0.240, 0.160). Pramipexole was least prone to wearing-off (0.109) and on-off fluctuation (0.041). Levodopa performed best in improvements of UPDRS-II, UPDRS-III, and UPDRS-II + III (0.925, 0.952, 0.934). Bromocriptine ranked first in total withdrawals and withdrawals due to adverse events (0.736, 0.751). Four DAs showed different adverse events profiles.
CONCLUSIONS: In the two non-ergot DAs, ropinirole is associated with a lower risk of dyskinesia while pramipexole is associated with lower risks of wearing-off and on-off fluctuations. Our research may facilitate head-to-head research, larger sample sizes, long following-up time RCTs to confirm the findings of this network meta-analysis.

We herein report the first case of constrictive pericarditis (CP) induced by long-term pergolide treatment for Parkinson\'s disease that was assessed using multimodal imaging in a 72-year-old patient with leg edema and dyspnea. The patient was correctly diagnosed with CP using multimodal imaging and successfully treated with pericardiectomy. The treatment history of Parkinson\'s disease and pathological findings of the removed pericardium suggested that long-term pergolide was the cause of CP. Properly recognizing pergolide as the cause of CP and accurately diagnosing CP using multimodal imaging may contribute to the early detection and treatment of pergolide-induced CP.

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.
METHODS: 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.

In horses/ponies with pituitary pars intermedia dysfunction (PPID), pergolide mesylate treatment, with monitoring of therapeutic response, is recommended by contemporaneous literature and equine endocrinologists. However, it is unknown whether these recommendations are adhered to in private practice. This clinical audit aimed to compare treatment and monitoring of PPID cases in veterinary practice against available recommendations. Case data and basal plasma adrenocorticotropic hormone (ACTH) concentrations from all equids tested for PPID between 2012 and 2016 from a single veterinary practice in the UK were obtained. Records were reviewed and information on treatment and monitoring over the subsequent 2-6 years was extracted and compared with published recommendations. After exclusions, the audit population was 480 animals (median age, 20 years). The most common presenting signs were laminitis and/or historical laminitis (51.2%) and hypertrichosis and/or delayed coat shedding (24.5%). Based on seasonally adjusted reference intervals for basal ACTH concentration, 51.7% (n = 248) of animals were classified as positive, 37.1% (n = 178) as negative and 11.3% (n = 54) as equivocal for PPID. Records were available for 459 animals; of which pergolide treatment was initiated in 78.7% (n = 185/235) of positive cases, 19.2% (n = 10/52) of equivocal cases and 6.4% (n = 11/172) of cases classified as negative. Overall, 87.2% (n = 129/148) of cases commenced treatment as per recommendations. Only 77.7% (n = 160/206) of pergolide-treated animals had documented PPID monitoring and of these, only 48.1% (n = 77/160) had follow-up basal ACTH testing in the first 1-3 months following diagnosis. The findings confirm that management of PPID in veterinary practice fell below contemporaneous recommendations, especially for monitoring.

Hyperinsulinemia associated with pituitary pars intermedia dysfunction (PPID) and/or equine metabolic syndrome is well documented to put horses at high risk of laminitis. While dietary control of simple sugars and starch is the most effective therapy to control hyperinsulinemia, some horses fail to respond.
Ten horses with hyperinsulinemia refractory to diet control, metformin, levothyroxine, and pergolide (if diagnosed with PPID) were treated with sodium-glucose cotransporter-2 inhibitor canagliflozin (Invokana®). Nine horses were hyperglycemic (>5.5 mmol/l) or had a history of hyperglycemia. Before instituting therapy, renal function was assessed by determining serum creatinine and blood urea nitrogen concentrations. Canagliflozin was administered orally once a day, with food. Dipstick urinalysis was performed every 2 weeks to confirm glucosuria and screen for proteinuria. Owners were also instructed regarding clinical signs consistent with urinary tract infection. All horses responded with a substantial decrease in serum insulin concentrations to normal or near normal values. Laminitis pain resolved in all cases, with regression of fat deposits. Owner satisfaction with outcomes was 100%.
Once daily administration of the SGLT2 inhibitor canagliflozin corrected hyperglycemia, reduced insulin to normal or near normal levels, and was 100% effective in reversing or reducing abnormal fat pads and eliminating laminitis pain in horses with refractory hyperinsulinemia and laminitis. The core aspects of therapy-diet control, exercise when possible, and adequate treatment of PPID-must also be maintained if using canagliflozin. Canagliflozin should be reserved for refractory cases. Further controlled trials to investigate canagliflozin pharmacokinetics, pharmacodynamics, efficacy, and safety are needed.

Thyrotropin releasing hormone (TRH) stimulation testing is often used to support a diagnosis of pituitary pars intermedia dysfunction (PPID) in horses although it is unclear whether or not repeat TRH stimulation testing post-treatment is a valid means of assessing response to medical therapy. Laboratory submissions from 64 suspected equine PPID cases were examined including the initial pre-treatment TRH stimulation test and a follow up test within 100 days of starting medical therapy with pergolide. In a subset of cases, further follow-up tests were examined beyond 100 days of starting treatment. Results from tests conducted between 1 July and 30 November were excluded. Significant improvements were seen in both the baseline and TRH-stimulated adrenocorticotrophic hormone (ACTH) concentrations within 100 days with no further improvements seen in the subset of cases examined thereafter. Although 88% (n = 56/64) of all cases showed a decreased response to TRH post-treatment, only 24% (n = 9/38) of horses with positive pre-treatment TRH stimulation tests normalised following treatment, with a further 34% (n = 13/38) improving into an equivocal test outcome category. Most commonly (42%; n = 16/38), horses with positive pre-treatment TRH stimulation tests remained positive following treatment, although 75% (n = 12/16) of these showed a numerically lower post-treatment response to TRH. These results will help inform practitioners of expected changes in TRH stimulation test results when assessing response of horses with PPID to medical therapy with pergolide.

Pathological angiogenesis is correlated with many ophthalmic diseases. The most common are exudative age-related macular degeneration and proliferative diabetic retinopathy. The current treatment for these diseases is based on regularly administered anti-VEGF antibodies injections. In the study, we investigated selected D2 dopaminergic receptor agonists, namely bromocriptine, cabergoline and pergolide, on hypoxia-induced neovascularization. We used the zebrafish laboratory model, specifically three-day post fertilization (dpf) Tg(fli-1: EGFP) zebrafish larvae. To induce abnormal angiogenesis of hyaloid-retinal vessels (HRVs) and intersegmental vessels (ISVs), the larvae were treated with cobalt chloride (II) (CoCl2) (a hypoxia-inducing agent) from 24 h post fertilization. The inhibitory role of D2 dopaminergic receptor agonists was investigated using confocal microscopy and qPCR. Additionally, the results were compared to those obtained in the group treated with CoCl2 followed by bevacizumab, the well-known antiangiogenic agent. Confocal microscopy analyses revealed severe deformation of vessels in the CoCl2 treated group, while co-incubation with bromocriptine, cabergoline, pergolide and bevacizumab, respectively, significantly inhibited abnormalities of angiogenesis. The qPCR analyses supported the protective role of the chosen dopaminergic agonists by demonstrating their influence on CoCl2-derived upregulation of vegfaa expression. The present results suggest that the D2 receptor agonists can be considered as a new direction in research for antiangiogenic therapy.

Pituitary neuroendocrine tumors (PitNET) are commonly benign tumors accounting for 10-25% of intracranial tumors. Prolactin-secreting adenomas represent the most predominant type of all PitNET and for this subtype of tumors, the medical therapy relies on the use of dopamine agonists (DAs). DAs yield an excellent therapeutic response in reducing tumor size and hormonal secretion targeting the dopamine receptor type 2 (D2DR) whose higher expression in prolactin-secreting adenomas compared to other PitNET is now well established. Moreover, although DAs therapy does not represent the first-line therapy for other PitNET, off-label use of DAs is considered in PitNET expressing D2DR. Nevertheless, DAs primary or secondary resistance, occurring in a subset of patients, may involve several molecular mechanisms, presently not fully elucidated. Dopamine receptors (DRs) expression is a prerequisite for a proper DA function in PitNET and several molecular events may negatively modify DR membrane expression, through the DRs down-regulation and intracellular trafficking, and DR signal transduction pathway. The current mini-review will summarise the presently known molecular events that underpin the unsuccessful therapy with DAs.

BACKGROUND: Pituitary pars intermedia dysfunction (PPID), a neurodegenerative disease leading to reduced dopamine production, is a common disease in aged horses. The treatment is based on administration of the dopamine agonist pergolide. This drug has been related to valvular fibrosis in humans, but the cardiovascular effect of this drug has not yet been investigated in horses.
OBJECTIVE: To determine whether pergolide induces valvular disease in horses or affects the cardiac function.
METHODS: Standard, tissue Doppler (TDE) and two-dimensional speckle tracking (STE) echocardiography were performed in horses with diagnosed PPID based on adrenocorticotropic hormone dosage. Measurements taken in horses treated with pergolide were compared with those from untreated horses with nonparametric t-tests. Furthermore, measurements from follow-up examinations performed at least three months after the initial exam were compared with a Wilcoxon signed rank test for repeated measurements in each group.
RESULTS: Twenty-three horses were included. None of the 12 horses under treatment developed valvular regurgitation. Furthermore, no differences in the measurements of the left ventricular systolic or diastolic function could be seen between the group of horses with treatment and those without treatment. Measurements taken in the follow-up exam did not differ compared to those taken in the initial exam in both groups.
CONCLUSIONS: No changes of the left ventricular function assessed by TDE and STE could be shown in a small population of horses with confirmed PPID. Treatment with pergolide did not affect the ventricular function nor induce valvular disease.