Iodine Deficiency
Iodine deficiency is seen in new born animals (lamb, kid, calf and piglet) of all species. Iodine is essential as a constituent of the thyroid hormones, in particular T3 and T4, and 80% of the iodine in the body is found in the thyroid gland.
Etiology
- Primary deficiency due to low iodine content in the soil.
- Secondary deficiency results from ingestion of the goitrogic substances like brassicas and legumes. Goitrogenic plants rich in thiocyanate. Thiocyanate in the rumen restricts the uptake of iodine by the thyroid.
- Iodine deficiency causes decreased T4 production and stimulation of TSH secretion, resulting in hyperplasia of the thyroid gland.
- Selenium is required for the conversion of T4 to active T3, and thus selenium deficiency may lead to secondary iodine deficiency states.
- Excess calcium in the diet and linseed meal also cause iodine
Clinical signs
- Thyroid gland enlargement is the classical sign of Iodine deficiency.
- Pregnant animal gives stillbirth, weak birth, alopecia and subcutaneous edema and death.
- Iodine with selenium cause poor growth rate, ill-thirft, low milk yield and retained placenta.
- In bulls decrease sex libido.
Differential diagnosis
- Selenium/Vitamin deficiency
- Congenital defect
- Hypothyroidism
Diagnosis
- Clinical signs: Severe goitre (enlargement of thyroid gland)
- Histopathology of thyroid gland confirm diagnosis
- Plasma inorganic iodine measurement– it is not reliable because value may alter by feed intake
- Estimation of T4 level is reliable (Normal T4 <20nmol/l; Iodine deficiency T4 >50nmol/l). T4 level elevated due to iodine deficiency secondary to goitrogenic substance, it prevents the conversion of T4 to T3.
Treatment
- Oral administration of potassium iodide is the treatment for Iodine deficiency.
Prevention and control
- Dietary supplementation
