Hypothyroidism

From Cow
Congenital goitre and alopecia in a pedigree Saler calf[1]

Bovine hypothyroidism ('goitre') is a rare genetic and sometimes nutritional disease of beef and dairy cattle worldwide and often associated with iodine deficient soils.

Hypothyroidism is the most common type of thyroid disorder in cattle and is caused by defective thyroglobulin synthesis and secretion[2]. This disease is rarely seen nowadays with feed supplements containing adequate dietary sources of iodine. Most cases arise as a congenital disease[3], developing as an idiopathic atrophy of the thyroid gland. There is some evidence that flouridation of cattle drinking water may contribute to this disease[4]. Lymphocytic thyroiditis has also been reported in cattle.

Hypothyroidism is rarely diagnosed in younger cattle except as an incidental finding. In clinically affected cattle, signs include recurrent hoof overgrowth, persistent anestrous, obesity, dull hair coat associated with symmetrical alopecia, and decreased activity level.

Induced hypothyroidism in superovulated Brahman cows showed markedly reduced milk production[5] but improved weight gain, body condition scores and fertility[6]. Some cattle, however, still display signs of oestrus after thyroidecty, suggesting oestrus is not solely regulated by thyrotropic mechanisms[7].

Diagnosis is usually based on presenting clinical signs supported by laboratory demonstration of elevated levels of total triiodothyronine and total thyroxine.

Treatment is usually successful with oral levothyroxine and monitoring improvement in clinical signs included weight loss, hair regrowth, and reproductive cycling[8].

References

  1. Watson, PJ & Scholes, SF (2010) Congenital goitre and alopecia in pedigree Saler cattle. Vet Rec 166:29-30
  2. Medeiros-Neto G et al (1993) Defective thyroglobulin synthesis and secretion causing goiter and hypothyroidism. Endocr Rev 14(2):165-183
  3. Guyot H et al (2007) Development and validation of a radioimmunoassay for thyrotropin in cattle. J Vet Diagn Invest 19(6):643-651
  4. Choubisa SL (1999) Some observations on endemic fluorosis in domestic animals in Southern Rajasthan (India). Vet Res Commun 23(7):457-465
  5. Thrift TA et al (1999) Effects of induced hypothyroidism on weight gains, lactation, and reproductive performance of primiparous Brahman cows. J Anim Sci 77(7):1844-1850
  6. Bernal A et al (1999) Effects of induced hypothyroidism on ovarian response to superovulation in Brahman (Bos indicus) cows. J Anim Sci 77(10):2749-2756
  7. Stewart RE et al (1993) Induction of estrus after thyroidectomy in nonlactating Holstein cows. J Dairy Sci 76(9):2619-2623
  8. Allender MC et al (2007) Hypothyroidism in an African forest buffalo (Syncerus caffer nanus). J Zoo Wildl Med 38(1):143-145