**4. Pathogenesis**

Inadequate iodine in the thyroid gland results in the synthesis of uniodinated inactive prehormone instead of the thyroxine, which stimulates the pituitary gland to secrete thyroidstimulating hormone (TSH). This commonly results in hyperplasia of the thyroid tissue and considerable enlargement of the gland, that is, goiter (**Figures 1** and **2**).

**5. Clinical findings**

of the glands [12, 13].

Iodine deficiency occurs in many species of animals and develops different signs in different animals. Goiter is a cardinal sign of iodine deficiency manifested mostly in young ones, that is, kids. The normal thyroid gland is 0.20% of body weight, but it is markedly enlarged up to the size of an orange in iodine-deficient goats [3]. The thyroid gland of goats/kids may be graded as palpable and plum size (+), easily palpable and lemon size (++), and duck egg size, hanging and visible from the distance (+++) (**Figure 3c**). Kids who survive the initial danger period after birth may recover except for partial persistence of goiter (**Figure 1**). The gland may pulsate with the normal arterial pulse and may extend down a greater part of the neck and cause some local edema. Auscultation and palpation of the jugular furrow may reveal the presence of a murmur and thrill (the thyroid thrill) due to the increased arterial blood supply

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**Figure 2.** Kid borne with goiter to an apparently normal goat (Courtesy of Dr. R.K. Bhardwaj).

Affected kids are born with enlarged thyroid gland or goiter, and enlargement of pituitary gland is also reported [14]. There may be birth of premature kids which are very weak and die within few hours of birth due to severe dyspnea caused by compression of the trachea by enlarged thyroid glands. Majority of new born kids may be hairless/bald (**Figure 3a**) or covered with very fine hair due hypoplasia of hair follicles [15]. Kids may appear dumb or unwilling to suckle the dam [3]. Growth rate of kids is stunted. Fertility of does is affected. Iodine supplementation in goats is found to increase conception, succeed in the first insemination,

and reduce abortion rate and dystocia due to goiter [16, 17].

**Figure 1.** Enlarged thyroid gland/congenital goiter in a kid presented to the University clinics (Courtesy of Dr. R.K.Bhardwaj).

**Figure 2.** Kid borne with goiter to an apparently normal goat (Courtesy of Dr. R.K. Bhardwaj).
