Adenomatous Hyperplasia of the Thyroid Gland in Beluga Whales (Delphinapterus leucas) from the St. Lawrence Estuary and Hudson Bay, Quebec, Canada

Retrospective comparison of thyroid hormones in Steller sea lions Eumetopias jubatus under professional care with and without thyroid disease

An evaluation of morbidity and mortality in Steller sea lions (SSLs) Eumetopias jubatus under professional care identified a high prevalence of thyroid disease in aged animals. While studies have investigated the effects of age, season, nutrition, stressors, and pollutants on thyroid hormones in pinnipeds, data from individuals with known thyroid disease are lacking. Histopathological reports of adult SSLs in North American aquariums from 1979 to 2022 with banked serum (n = 14) were reviewed. Radioimmunoassays, which have been validated in this species, were used to determine triiodothyronine (TT3), total thyroxine (TT4), and free thyroxine (fT4). A solid-phase chemiluminescent immunometric assay for thyroid-stimulating hormone (TSH) quantification was validated by testing inter- and intra-assay repeatability, recovery, and parallelism. Lesions included follicular cysts (n = 5), adenoma with thyroglossal duct or follicular cysts (n = 2), medullary or follicular C-cell carcinoma with follicular cysts and nodular hyperplasia (n = 1), neuroendocrine carcinoma with follicular cysts (n = 1), and sarcomatoid carcinoma metastasis to the thyroid (n = 1). Significantly lower concentrations of TT3, TT4, and fT4 in SSLs with thyroid disease (n = 10) versus those without (n = 4) were attributed to space-occupying lesions, advanced age, and/or season. TSH was not significantly different between groups. Fifty percent of diseased SSL profiles were within reference ranges, and all individuals with lesions were clinically euthyroid. These data expand the current understanding of thyroid disease in SSLs and underscore the need for additional diagnostics (e.g. cervical ultrasound) concurrently with hormone assays to effectively screen for underlying abnormalities.

Persistent Mü̈llerian duct syndrome in a beluga whale Delphinapterus leucas

This case study describes a persistent Mü̈llerian duct syndrome (PMDS), a rare form of XY disorder of sex development (DSD), in a mature (>15 yr) beluga whale Delphinapterus leucas. The phenotypically and genetically male beluga whale had both Mü̈llerian (paramesonephric) and Wolffian (mesonephric) duct derivatives. A mild hydrometra was present. Gross and histological analyses indicated the testes were atrophied. Histopathologic findings in the testes also included fibrosis in addition to ductus deferens ductular dilation, epididymal ductular dilation, lymphoplasmacytic balanitis, uterine glandular atrophy, and endometrial fibrosis. DSDs are rarely reported in cetaceans, and PMDS has never been described in a cetacean.

Circulating thyroid hormones and associated metabolites in white whales (Delphinapterus leucas) determined using isotope-dilution mass spectrometry

Blood was sampled from nine free-ranging white whales (beluga whale, Delphinapterus leucas) from Svalbard, Norway during the summers of 2013 and 2014. Total concentrations of eleven thyroid hormones and metabolites were measured in serum using a novel liquid chromatography tandem mass spectrometry analytical method. Measurements of these compounds in plasma gave the same results as in serum. The three hormones found in highest concentrations were 3,3',5-triiodothyronine (T₃), 3,3',5'-triiodothyronine (rT₃) and thyroxine (T₄). Traces of associated metabolites were also found.

Acute and Chronic Gas Bubble Lesions in Cetaceans Stranded in the United Kingdom

The first evidence suggestive of in vivo gas bubble formation in cetacea, including eight animals stranded in the UK, has recently been reported. This article presents the pathologic findings from these eight UK-stranded cetaceans and two additional UK-stranded cetacean cases in detail. Hepatic gas-filled cavitary lesions (0.2-6.0 cm diameter) involving approximately 5–90% of the liver volume were found in four (two juvenile, two adult) Risso's dolphins ( Grampus griseus), three (two adult, one juvenile) common dolphins ( Delphinus delphis), an adult Blainville's beaked whale ( Mesoplodon densirostris), and an adult harbour porpoise ( Phocoena phocoena). Histopathologic examination of the seven dolphin cases with gross liver cavities revealed variable degrees of pericavitary fibrosis, microscopic, intrahepatic, spherical, nonstaining cavities (typically 50–750 μm in diameter) consistent with gas emboli within distended portal vessels and sinusoids and associated with hepatic tissue compression, hemorrhages, fibrin/organizing thrombi, and foci of acute hepatocellular necrosis. Two common dolphins also had multiple and bilateral gross renal cavities (2.0–9.0 mm diameter) that, microscopically, were consistent with acute ( n = 2) and chronic ( n = 1) arterial gas emboli-induced renal infarcts. Microscopic, bubblelike cavities were also found in mesenteric lymph node ( n = 4), adrenal ( n = 2), spleen ( n = 2), pulmonary associated lymph node ( n = 1), posterior cervical lymph node ( n = 1), and thyroid ( n = 1). No bacterial organisms were isolated from five of six cavitated livers and one of one cavitated kidneys. The etiology and pathogenesis of these lesions are not known, although a decompression-related mechanism involving embolism of intestinal gas or de novo gas bubble (emboli) development derived from tissues supersaturated with nitrogen is suspected.

Evaluation of two-dimensional and three-dimensional ultrasound in the assessment of thyroid volume of the Indo-Pacific bottlenose dolphin (Tursiops aduncus)

The assessment of thyroid volume plays an indispensable role in the diagnosis and management of different thyroid diseases. The present study evaluates the accuracy of dolphin thyroid volume measurement as determined by four two-dimensional (2D) ultrasound methods (A-D), with a standard of reference using three-dimensional (3D) ultrasound. The measurement accuracy for different recognized thyroid configuration is also evaluated. Inter- and intraoperator variability of the measurement methods was determined. Thyroid ultrasound examinations were conducted in 16 apparently healthy Indo-Pacific bottlenose dolphins (Tursiops aduncus) with 2D and 3D ultrasound under identical scanning conditions. All 2D ultrasound measurement methods yielded high accuracies (79.9-81.3%) when compared with the 3D ultrasound measurement, and had high measurement reproducibility (77.6-86.2%) and repeatability (78.1-99.7%). For 2D ultrasound measurements, Methods A and B were more accurate and reliable than Methods C and D, regardless of thyroid configuration. Ultrasound is useful in the measurement of thyroid volume in bottlenose dolphins. For the first time, a reliable ultrasound scanning protocol for measuring dolphin thyroid volume was developed, which provides a means to establish a normative reference for the diagnosis of thyroid pathologies and to monitor the thyroid volume during the course of treatment in living dolphins. Key words: 3D ultrasound, Indo-Pacific bottlenose dolphin, thyroid volume measurement, Tursiops aduncus.

A comparison of portable ultrasound and fully-equipped clinical ultrasound unit in the thyroid size measurement of the Indo-Pacific bottlenose dolphin

Measurement of thyroid size and volume is a useful clinical parameter in both human and veterinary medicine, particularly for diagnosing thyroid diseases and guiding corrective therapy. Procuring a fully-equipped clinical ultrasound unit (FCUS) may be difficult in most veterinary settings. The present study evaluated the inter-equipment variability in dolphin thyroid ultrasound measurements between a portable ultrasound unit (PUS) and a FCUS; for both units, repeatability was also assessed. Thyroid ultrasound examinations were performed on 15 apparently healthy bottlenose dolphins with both PUS and FCUS under identical scanning conditions. There was a high level of agreement between the two ultrasound units in dolphin thyroid measurements (ICC = 0.859-0.976). A high intra-operator repeatability in thyroid measurements was found (PUS: ICC = 0.854-0.984, FCUS: ICC = 0.709-0.954). As a conclusion, no substantial inter-equipment variability was found between PUS and FCUS in dolphin thyroid size measurements under identical scanning conditions, supporting further application of PUS for quantitative analyses of dolphin thyroid gland in both research and clinical practices at aquarium settings.

Disruptive effects of persistent organohalogen contaminants on thyroid function in white whales (Delphinapterus leucas) from Svalbard

We analysed levels of 56 organohalogen contaminants (OHCs) including brominated flame retardants, polychlorinated biphenyls (PCBs), and organochlorine pesticides in the blubber of white (beluga) whales (Delphinapterus leucas) from Svalbard, Norway (N=12; 6 adults [5 males and 1 female] and 6 subadults [4 males and 2 females]) collected in 1996-2001. We also measured circulating levels of thyroid hormones (THs) and thyroid stimulating hormone (TSH) in the whales. The results confirm that OHC levels in these white whales are among the highest levels recorded in wildlife from Svalbard, and at the high end of the range when compared to white whales from the North American Arctic. A projection to latent structure (PLS) model (subadults and adult males grouped together) revealed that known or suspected thyroid disruptive contaminants (polybrominated diphenylether [PBDE]-28, -47, -99, -100, and -154, hexachlorobenzene [HCB], and PCB-105) were negatively correlated with circulating levels of total thyroxin (TT4), free T4 (FT4) and free triiodothyronine (FT3). Most of these negative relationships were also confirmed using partial correlations controlling for length (and thus age) of the whales. The positive correlations of TT4, FT4 and FT3 with hexabromocyclododecane (HBCD), α-hexachlorocyclohexane (α-HCH), chlorinated bornanes CHB-40 and CHB-62 revealed by the PLS model were not confirmed by partial correlations. TH levels in the present study appeared to be somewhat lower than levels measured in beluga whales from the Canadian Arctic. However, we were not able to determine if this was caused by different levels of OHCs, or differences in biological factors (e.g. age, sex, moulting status, and season) and analytical methods between the studies. Although the sample sizes were low and statistical models cannot depict the biological cause-effect relationships, this study suggests negative influences of specific OHCs, particularly PBDEs, on thyroid hormone levels in white whales. The impact this might have on individual and population health is unknown.

Proliferative thyroid lesions and hyperthyroidism in captive fishers (Martes pennanti)

Diseases of the thyroid gland are common in many zoo species, but there are few descriptions of thyroid dysfunction in Mustelidae. A 7-yr-old, captive-bred female fisher (Martes pennanti) with progressive alopecia was diagnosed with clinical hyperthyroidism based on persistent elevation of both total and free serum thyroxine and triiodothyronine, ultrasound examination, and histologic evidence of adenomatous hyperplasia. Four additional geriatric adult fishers (two male and two female) were identified with thyroid adenomatous hyperplasia in a review of 23 postmortem records. Banked sera were available for thyroid hormone testing from three of the four necropsy cases. Total and free thyroxine were elevated in four of four animals tested, and triiodothyronine was elevated in two of three animals tested. Necropsy findings in four cases identified cardiac hypertrophy, congestive heart failure, and vascular lesions consistent with hypertension; complete tissues were not available from the remaining case. Clinical and subclinical hyperthyroidism may be a common but overlooked condition of captive fishers.

Health effects from long-range transported contaminants in Arctic top predators: An integrated review based on studies of polar bears and relevant model species

The aim of this review is to provide a thorough overview of the health effects from the complexed biomagnified mixture of long-range transported industrial organochlorines (OCs), polybrominated diphenyl ethers (PBDEs), perfluorinated compounds (PFCs) and mercury (Hg) on polar bear (Ursus maritimus) health. Multiple scientific studies of polar bears indicate negative relationships between exposure to these contaminants and health parameters; however, these are all of a correlative nature and do not represent true cause-and-effects. Therefore, information from controlled studies of farmed Norwegian Arctic foxes (Vulpes lagopus) and housed East and West Greenland sledge dogs (Canis familiaris) were included as supportive weight of evidence in the clarification of contaminant exposure and health effects in polar bears. The review showed that hormone and vitamin concentrations, liver, kidney and thyroid gland morphology as well as reproductive and immune systems of polar bears are likely to be influenced by contaminant exposure. Furthermore, exclusively based on polar bear contaminant studies, bone density reduction and neurochemical disruption and DNA hypomethylation of the brain stem seemed to occur. The range of tissue concentration, at which these alterations were observed in polar bears, were ca. 1-70,000 ng/g lw for OCs (blood plasma concentrations of some PCB metabolites even higher), ca. 1-1000 ng/g lw for PBDEs and for PFCs and Hg 114-3052 ng/g ww and 0.1-50 microg/g ww, respectively. Similar concentrations were found in farmed foxes and housed sledge dogs while the lack of dose response designs did not allow an estimation of threshold levels for oral exposure and accumulated tissue concentrations. Nor was it possible to pinpoint a specific group of contaminants being more important than others nor analyze their interactions. For East Greenland polar bears the corresponding daily SigmaOC and SigmaPBDE oral exposure was estimated to be 35 and 0.34 microg/kg body weight, respectively. Furthermore, PFC concentrations, at which population effect levels could occur, are likely to be reached around year 2012 for the East Greenland polar bear subpopulation if current increasing temporal trends continue. Such proposed reproductive population effects were supported by physiological based pharmacokinetic (PBPK) modelling of critical body residues (CBR) with risk quotients >or=1 for SigmaPCB, dieldrin, SigmaPFC and SigmaOHC (organohalogen contaminant). The estimated daily TEQ for East Greenland polar bears and East Greenland sledge dogs were 32-281-folds above WHO SigmaTEQ guidelines for humans. Compared to human tolerable daily intake (TDI), these were exceeded for PCBs, dieldrin, chlordanes and SigmaHCH in East Greenland polar bears. Comparisons like these should be done with caution, but together with the CBR modelling and T-score estimations, these were the only available tools for polar bear risk evaluation. In conclusion, polar bears seem to be susceptible to contaminant induced stress that may have an overall sub-clinical impact on their health and population status via impacts on their immune and reproductive systems.

Chronic dietary exposure to environmental organochlorine contaminants induces thyroid gland lesions in Arctic foxes (Vulpes lagopus)

The impact of dietary organochlorine (OC) exposure on thyroid gland pathology was studied in farmed male Arctic foxes (Vulpes lagopus). The exposed group (n=16) was fed a diet based on wild minke whale (Balaenoptera acutorostrata) blubber as a main fat source in order to mimic the exposure to OC cocktails in the Artic environment. This resulted in an exposure of approximately 17 microg Sigma OC/kg day and a Sigma OC residue adipose tissue and liver concentration of 1700 and 4470 ng/gl.w., respectively, after 16 months of exposure. Control foxes (n=13) were fed a diet with pork (Sus scrofa) fat as a main fat source containing significantly lower OC concentrations. The food composition fed to the control and exposed group was standardized for nutrient contents. Four OC-related histopathological changes were found: (1) flat-epithelial-cell true thyroid cysts (TC) characterized by neutral content; (2) remnants of simple squamous epithelial-cell embryonic ducts containing neutral debris (EDN); (3) remnants of stratified squamous epithelial-cell embryonic ducts containing acid mucins often accompanied with debris of leukocyte inflammatory nature (EDM) and (4) disseminated thyroid C-cell hyperplasia (HPC). Of these, the prevalence of TC, EDN and HPC was significantly highest in the exposed group (chi(2) test: all p<0.04). The study shows that the OC mixture in minke whale blubber may cause development of thyroid gland cysts, C-cell hyperplasia and increase the prevalence of cystic remnants of embryonic ducts. The mechanism causing these effects could include endocrine disruption of the hypothalamus-pituitary-thyroid (HPT) axis, a disturbance of the calcium homeostasis/metabolism or energy metabolism or immune suppression. Because concentrations of OCs are higher in wild Arctic foxes, it is likely that these animals could suffer from similar OC-induced thyroid gland pathological and functional changes.

The Thyroid Gland in Bottlenose Dolphins (Tursiops truncatus) from the Texas Coast of the Gulf of Mexico: Normal Structure and Pathological Changes

Fresh thyroid glands (n=60) from Atlantic bottlenose dolphins that died after stranding along the Texas coast between 1991 and 2005 were examined. Organ weight ranged from 11 g in a neonate (length 109 cm) to 58 g in a large (249 cm) male. More typical weights were 25-45 g (mean=30.6 g). Glands tended to be larger in pregnant and lactating females (mean 37.4 g; n=5) than in non-pregnant animals of comparable size. In infancy, the gland tended to be compact, relatively homogeneous, and sometimes partly lobular, but with advancing age it became more lobular, the lobules being defined by fibrous bands. In one 8-year-old female (233 cm), and in a large male (295 cm) aged>25 years the gland was represented by a cluster of lobules. Lobulation was not necessarily accompanied by increased weight, distinguishing it from hyperplasia. With age, variation in follicle size and colloid density tended to increase. Two animals (3%) had adenomas and five (8%) had discrete hyperplastic nodules, not to be confused with lobulation. Five (8%) had macroscopically identifiable colloid-filled cysts (1-4 mm in diameter). Nine animals (15%) had squamous cysts (4-15 mm) containing creamy white fluid. Other abnormalities included patchy or diffuse interstitial fibrosis (six cases, 10%) amyloidosis (two cases), thyroiditis (one case) and vasculitis (one case). No malignant neoplasms were found. Cells presumed to be C cells (light cells, parafollicular cells) were identified immunohistochemically with synaptophysin antibody.

AhR-agonist-induced transcriptional changes of genes involved in thyroid function in primary porcine thyrocytes

The Ah receptor (AhR) is a ligand transcription factor mediating toxic effects of chemicals such as dioxins. The 2,3,7,8 tetrachlorodibenzo-p-dioxin (TCDD) and the coplanar polychlorinated biphenyl 126 (PCB 126) are member of the polyhalogenated aromatic hydrocarbons family exerting a variety of toxic effects in a tissue-specific and species-specific manner including thyroid function. In the present study, we aimed to investigate the effects of TCDD (1 and 10 nM) and dioxin-like PCB 126 (306 nM) on the AhR signaling pathway and on the gene expression profiles of key factors involved in thyroid function, including thyroglobulin (TG), thyroid peroxidase (TPO), the sodium iodide symporter (NIS), TSH receptor (TSHR), and cathepsins (Cat B and L), using a primary porcine thyrocyte culture as the experimental model. AhR and ARNT expression was detected both as mRNA and on the protein level. Expression did not vary upon treatment with either TCDD or PCB 126. However, treatment with TCDD and PCB 126 induced an AhR signaling response, as indicated by the expression of the AhR-target gene cytochrome P-450 1A1 (CYP1A1). Both 10 nM TCDD and PCB 126 treatment induced a significant downregulation in the expression of NIS and cathepsin B without affecting any of the other parameters investigated. In conclusion, these data indicate that (a) thyrocytes are targets of TCDD and TCDD-like compounds and (b) there is evidence for two independent most likely AhR-mediated molecular mechanisms, by which these compounds negatively interfere with thyroid function.