CLINICAL, DIAGNOSTIC AND THERAPEUTIC STUDIES OF HYPOTHYROIDISM IN DOGS

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2010-08
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SRI VENKATESWARA VETERINARY UNIVERSITY TIRUPATI - 517 502. (A.P.) INDIA
Abstract
ABSTRACT : Out of a total 10,172 dogs presented to the small animal medical ward of Veterinary Hospital, Bhoiguda, Teaching Veterinary Clinical Complex, College of Veterinary Science, Rajendranagar, Hyderabad, 47 were found hypothyroid. The overall prevalence of hypothyroidism in dogs was 0.46 per cent and it was 30.92 per cent among dogs exhibiting clinical manifestations suggestive of impaired thyroid function. The highest prevalence was recorded in Labrador Retriever (25.53 per cent) aged between 5-10 yrs (61.70 per cent) and spayed females (40.43 per cent) and lowest in Daschund and Pug (2.13 per cent), less than 5 yrs (6.83 per cent) and uncastrated males (12.77 per cent). The common clinical manifestations were bilateral alopecia (82.98 per cent), rat tail appearance (72.34 per cent), puppy like coat (17.02 per cent), dry and lustreless coat (68.08 per cent), secondary skin disorders (76.60 per cent), exercise intolerance (78.72 per cent), dyspnoea at rest (25.53 per cent), obesity (68.08 per cent), lethargy in (74.47 per cent), corneal lipidosis (10.64 per cent), goitre and lameness (10.64 per cent), pale mucosa (19.25 per cent), anaemia (27.6 per cent), nervous signs (25.53 per cent) and cyanosis and myxedema (8.51 per cent). The primary disorders associated with hypothyroid dogs were related to skin and coat in 76.60 per cent, and were mainly of Malassezia pachydermatis or Demodex canis or pyoderma. Further, certain systemic disorders such as cardiovascular, nervous system, diabetes mellitus, renal and musculoskeletal disorders were also recorded. Severely affected hypothyroid dogs were presenting the severe signs related to both skin and coat and reduced metabolic rate. Whereas, dogs presented with only skin and coat abnormalities were considered mild and those presented with predominant skin and coat and mild to moderate reduced metabolic rate associated signs were diagnosed as moderately affected ones. Out of 23 dogs in group I, alleviation of clinical signs occurred in 21 following 30-35 days of treatment with levothyroxine. The remaining two dogs presenting goitre, cyanosis and myxedema, severe nervous signs, pale mucosae and corneal lipidosis died after 10 and 15 days of initiation of therapy. Whereas, group II dogs treated with levothyroxine and carnitine showed clinical improvement from day 15 and complete alleviation of signs were recorded by day 30. No death was recorded in this group of dogs. All the hypothyroid dogs revealed normocytic, normochromic and non-regenerative anaemia with non-significantly different parameters except PCV. Similarly, there was hypercholesterolemia, hypertriglyceridemia with elevated levels of CKMB, LDH, ALP and TSH with significantly low levels of TT4, fT4 and T3. The thyroid lobes of the affected dogs were heterogenous, had an irregular thick capsule, ill-delineated abnormal shape, smaller size and were hyper echoic compared with sternothyroid muscles on day 0. Whereas, the mean length, width, height and volume of the hypothyroid lobes were significantly decreased when compared to apparently healthy dogs. No significant difference was noticed with these findings following therapy. The mean pre treatment values of LVEdD and LVEsD of both the groups were significantly increased (p<0.01) when compared with the mean values of healthy dogs. These dimensions after therapy were found to be significantly (p<0.05) different from the findings recorded prior to the treatment. The other dimensions viz., LVPWd, LVPWs, IVSd, IVSs, and EPSS of group I and II, were also different significantly (p<0.05) from that of healthy dogs. Following therapy (on day 45) there was a non-significant difference in these values. With respect to ejection fraction and fractional shortening, a significantly low (p<0.01) levels were noticed in all the hypothyroid dogs. However, a significant (P<0.05) increase was recorded in these values on day 45 post therapy. Whereas, no specific difference in severity and intensity of turbulence and mosaic pattern of colour flow was noticed on pulse wave and colour flow Doppler of mitral valve in all the dogs before and after treatment. There was no significant difference in various haematological parameters such as TEC, Hb, PCV, TLC and DLC between the groups I and II. A significant difference was noticed in the values of CKMB and LDH (P<0.01) and cholesterol, triglycerides, total thyroxine, free thyroxine, triodothyronine and thyroid stimulating hormone (P<0.05) of group II dogs on day 45 after treatment as compared with group I. Whereas, no significant difference was noticed with the values of ALT and ALP in between the groups on day 45. The different abnormalities associated with thyroid gland morphology and texture that revealed during thyroid lobe ultrasonography such as irregular thick capsule, ill delineated, abnormal shape, smaller size, echogenic difference and thyroid lobe volume were not significantly different between the
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