The effects of thyroxine on hair growth in the dog

The effects of orally and topically administered thyroxine on hair growth were studied in normal, intact, cross-bred male dogs maintained under the same controlled conditions of temperature and photoperiod. It was found that, irrespective of the route of administration, thyroxine produced an increase in both the rate of hair growth and in the number of hair follicles entering the anagen phase of the hair cycle. With orally administered thyroxine, the changes in hair growth were most marked in the flank region.     

A study of normal hair growth in the dog

The rate of hair growth in the forehead, shoulder and flank regions of four normal-coated, cross-bred, male dogs maintained under the same controlled conditions of photoperiod, ambient temperature and diet, was measured during two six-week periods, one during summer and the other in winter. It was found that the rate of hair growth varied between individual dogs and also between the different regions in the same dog. Growth rate was most rapid in the shoulder region, followed by the flank and then the forehead regions, and was slightly more rapid in the shoulder and flank regions of three of the dogs during summer than in winter. Possible explanations for these variations in hair growth rate are discussed.     

Tertiary hypothyroidism in a dog

: A nine-year-old male entire Labrador was diagnosed with pituitary dependent hyperadrenocorticism. Following seven months of successful mitotane therapy, the dog presented with marked weight gain, seborrhoea and alopecia. Routine clinicopathological analyses revealed marked hypercholesterolaemia. Serum total and free thyroxine (T4) concentrations were below their respective reference ranges. Serum thyroid stimulating hormone (cTSH) concentration was within reference range. TSH and thyrotropin releasing hormone (TRH) response tests revealed adequate stimulation of total T4 in both, and cTSH in the latter test. Magnetic resonance imaging revealed a mass arising from the pituitary fossa, with suprasellar extension. A diagnosis of tertiary hypothyroidism was made. Following four weeks of levothyroxine therapy, circulating cholesterol concentration had declined, weight loss had ensued and dermatological abnormalities had improved. Euthanasia was performed four months later due to the development of neurological signs. A highly infiltrative pituitary adenoma, with effacement of the overlying hypothalamus was identified on post mortem examination. Tertiary hypothyroidism has not been previously reported in dogs.     

Juvenile-onset hypothyroidism in a dog

Juvenile-onset hypothyroidism was diagnosed in an adult mixed-breed dog examined because of quadraparesis. Unusual clinical signs attributable to juvenile-onset or congenital hypothyroidism included disproportionate dwarfism; enlarged, protruding tongue; mental dullness; and retention of a "puppy" coat, which was soft and fluffy, without guard hairs. Radiography of the vertebral column and long bones revealed multiple areas of delayed epiphyseal closure and epiphyseal dysgenesis. Myelography demonstrated several intervertebral disk protrusions in the cervical and lumbar regions. Hypothyroidism was confirmed on the basis of a low basal serum thyroxine concentration that failed to increase after the administration of thyroid stimulating hormone. Other laboratory abnormalities included nonregenerative, normocytic, normochromic anemia; mild hypercalcemia; and an impaired growth hormone (GH) secretory response after xylazine administration. At necropsy, the thyroid gland was small and weighed only 0.2g. Microscopic examination of the thyroid gland revealed a loss of glandular tissue, which was replaced by adipose tissue along its periphery. Gross or microscopic abnormalities were not noted in the pituitary gland, and immunohistochemical staining of the pituitary gland revealed a normal number of GH-containing acidophils. This suggests that primary hypothyroidism may result in an impaired secretion of growth hormone, and that pituitary dwarfism or GH deficiency may be difficult to differentiate from hypothyroid dwarfism on the basis of provocative GH testing alone.     

Congenital hypothyroidism in a boxer dog

Congenital central hypothyroidism was diagnosed in a one-year-old boxer dog. The dog was presented for investigation of lameness, lethargy and obesity. Survey skeletal radiographs revealed delayed bone maturation and epiphyseal dysgenesis. A diagnosis of hypothyroidism was confirmed on the basis of a low basal serum thyroxine (T₄) concentration that failed to increase following bovine thyroid stimulating hormone (TSH) administration. However, repeated administration of TSH resulted in reactivation of the thyroid gland suggesting a central rather than a primary problem. Consistently low basal plasma Cortisol concentrations were suggestive of a concurrent secondary or tertiary hypoadrenocorticism. Surprisingly, plasma growth hormone concentrations were elevated before treatment but decreased once thyroid replacement therapy had commenced.     

Hypercalcaemia in a dog with primary hypothyroidism

A 7-year-old female beagle was evaluated for symptomatic hypercalcaemia and primary hypothyroidism. Clinical findings were typical for hypothyroidism. Plasma parathyroid hormone was low and obvious causes for the hypercalcaemia were ruled out by means of abdominal ultrasonography, ultrasonography of the parathyroid glands, survey thoracic radiographs, and fine needle aspirate cytology of the spleen, liver, and peripheral lymph nodes. Treatment with thyroxine resulted in resolution of the hypercalcaemia after approximately 9 weeks of therapy. This is the 1st report of primary adult-onset hypothyroidism associated with symptomatic hypercalcaemia in a dog.     

Cutaneous mucinous vesiculation in a dog with hypothyroidism

Hypothyroidism was documented in an overweight dog with bilateral entropion, blepharoptosis, and multiple, non-inflammatory papular and vesicular lesions on the head. Histologic evaluation of skin biopsy specimens confirmed the diagnosis of mucinous vesiculation. All skin and eyelid abnormalities resolved in response to thyroid hormone supplementation.     

Primary hypothyroidism associated with leishmaniasis in a dog

A case of primary hypothyroidism associated with leishmaniasis is described in a four-year-old, male Yorkshire terrier. Clinical diagnosis of hypothyroidism was confirmed by a low baseline serum tetraiodothyronine (T4), a reduced response to thyroid-stimulating hormone (TSH) stimulation, an increased serum TSH concentration, and scintigraphic thyroid gland examination. Examination of a thyroid biopsy showed many Leishmania amastigotes, both inside and outside of macrophages, together with signs of follicular atrophy.     

扮靓狗狗有办“发”

狗狗的衣饰打扮,绝对紧贴我们的时装潮流,之前有彩甲,现在又有从日本传来的接发。将七彩斑斓的发饰,诸如羽毛、胶珠仔、皮绳系在毛发上,要多抢眼有多抢     

The contribution of stem cells to epidermal and hair follicle tumours in the dog

Background –  Although cutaneous stem cells have been implicated in skin tumourigenesis in humans, no studies have been conducted to elucidate the presence and the possible role of stem cells in hair follicle tumours in the dog. Hypothesis –  Stem cell markers are expressed in canine epidermal and follicular tumours and can be used to better understand the biology and origin of these tumours. Animals and Methods –  In the present study, normal skin sections and 44 follicular tumours were retrospectively investigated for the immunohistochemical expression of keratin 15 (K15) and nestin. In addition, 30 squamous cell carcinomas were evaluated for K15 expression. Results –  In normal skin, K15 and nestin were expressed in the outer root sheath cells of the isthmic portion of the hair follicle (bulge region), and K15 expression was also scattered in the basal cell layer of the epidermis. Infundibular keratinizing acanthomas, pilomatricomas and squamous cell carcinomas were mostly negative for K15, trichoblastomas were moderately to strongly positive, tricholemmomas were either negative or strongly positive, and trichoepitheliomas had heterogeneous staining. Nestin expression was generally faint in all follicular tumours. Conclusions and clinical importance –  Our results show that K15 can be a reliable marker for investigating the role of stem cells in hair follicle tumours of the dog, while nestin was judged to be a nonoptimal marker. Furthermore, our study suggests that hair follicle stem cells are present in the bulge region of hair follicles and could possibly play a role in tumourigenesis of canine tumours originating from this portion of the follicle, namely trichoblastomas, tricholemmomas and trichoepitheliomas. The loss of K15 expression in squamous cell carcinomas compared with normal skin suggests that this event could be important in the malignant transformation.     

The reaction of hair follicles in the vicinity of full-thickness excised skin wounds in the dog

The changes which take place in hair follicles close to full-thickness excised skin wounds in the thoracic and metatarsal regions of the dog are described. The follicles make a significant contribution to the bulk of epithelial cells which are capable of migrating to form the new epidermis, and their behaviour explains why the migrating epithelium is first seen to grow on to the surface of the wound in the sector which lies in the direction of hair flow, and why a zone of alopecia surrounds the excised wound.     

你知道犬为什么会有不同毛色吗

毛色是犬的遗传性状,在观赏、品种鉴定、育种中占有很重要的地位,由于上万年的品种分化和不同目的的人工选择,形成了现在丰富的毛色多样性,很多品种都有几种毛色。     

Clinical hypothyroidism associated with trimethoprim-sulfadiazine administration in a dog

Treatment of a 9-year-old spayed female mixed-breed dog with trimethoprim-sulfadiazine for a prolonged period resulted in clinical signs of hypothyroidism, and results of thyroid gland function tests were indistinguishable from those associated with endogenous hypothyroidism. Drug-induced hypothyroidism was diagnosed on the basis of history, normal thyroid uptake of sodium pertechnetate, and complete recovery of thyroid gland function after administration of trimethoprim-sulfadiazine was discontinued.     

Myasthenia gravis and hypothyroidism in a dog with meningomyelitis

A 12-year-old, spayed female miniature poodle was evaluated because of a 4-day history of paraparesis, dysuria, and tenesmus. Neurological assessment suggested peripheral nervous system dysfunction, predominantly pelvic limb weakness with a possible concurrent sixth lumbar (L(6)) to second sacral (S(2)) myelopathy. Further studies supported the diagnoses of myasthenia gravis, hypothyroidism, and meningomyelitis. To the authors' knowledge, this is the first reported case of concurrent myasthenia gravis and meningomyelitis in the dog. It was unclear whether the identified conditions evolved from a shared etiopathogenesis or were merely coincidental.     

L-thyroxine responsive cricopharyngeal achalasia associated with hypothyroidism in a dog

An eight-year-old, male boxer dog was presented with a one-month history of hindlimb weakness followed by compulsive ineffective drinking, dysphagia, regurgitation and nasal reflux during drinking. A neurological examination revealed weakness and conscious proprioception deficits in both hindlimbs with normal spinal reflexes. The dog's swallowing function was examined by fluoroscopy. This showed normal prehension of the barium paste, bolus formation and contraction of the pharyngeal muscle, but no opening of the upper oesophageal sphincter was detected. A serum thyroid stimulating hormone level of 0.402 ng/dl and serum total T4 of 0-01 microg/dl were determined. The dog fully recovered one month after L-thyroxine therapy. The association found between cricopharyngeal achalasia and hypothyroidism suggests that hypothyroidism should be included in the list of differential diagnoses for dogs with cricopharyngeal achalasia.