Iodine deficiency disorders

Spectrum of pathologies and risk groups

A lack of iodine in the body leads to the development of a number of pathologies, among which diffuse and nodular goiter, as well as iodine-deficiency hypothyroidism, are distinguished. Disorders of physical growth and development in children deserve special attention.

Children and pregnant women are the groups most vulnerable to iodine deficiency. A lack of this trace element in the population reliably increases the infant mortality rate. Neurocognitive consequences are of enormous importance: in regions endemic for iodine deficiency, indicators of mental development in the child population are reduced on average by 10–15%.

Intrauterine impact is also critical: if the mother did not receive enough iodine during pregnancy, it can manifest as a congenital enlargement of the thyroid gland in the newborn. The extreme degree of iodine deficiency leads to the development of cretinism—a severe condition characterized by gross and completely irreversible impairments in both physical and mental development.

Iodine prophylaxis strategies

Since iodine deficiency disorders are entirely preventable, clear prevention strategies have been developed:

• Mass prophylaxis. According to WHO recommendations, the optimal method is the use of iodized table salt. The rationale for this method is simple: salt is consumed daily by all segments of the population in quantities that physiologically correspond to age requirements. This method is economically affordable, and the risk of a serious iodine overdose is completely excluded.
• Individual prophylaxis. Consists of prescribing pharmacological iodine preparations to representatives of risk groups who have an increased requirement for this trace element (primarily children and pregnant women).
• Prevention during pregnancy. At the family planning stage and directly during gestation, a woman requires an additional intake of 250 mcg of iodine per day. This can be achieved through the prescription of potassium iodide monopreparations or the use of specialized vitamin and mineral complexes.

Consumption standards (WHO criteria, 2007)

The World Health Organization has established the following physiological norms and upper limits for safe iodine intake:

1. Pregnant and lactating women: the physiological requirement is 250 mcg/day. The upper limit (excessive intake) starts from 500 mcg/day.
2. Young children (up to 2 years old): the physiological requirement is 90 mcg/day. The upper limit is more than 180 mcg/day.

The intake of iodine preparations must be continuous throughout the entire pregnancy and the entire period of lactation. During breastfeeding, the maternal organism is the sole source of iodine for the infant. If the child is transferred to formula feeding, their requirement for the trace element is met through the composition of adapted infant formulas.

Endocrine regulation of child growth

Full-fledged growth of a child is impossible without adequate function of the endocrine system. Although the growth process has a multifactorial nature and depends on exogenous and endogenous influences, hormones play a leading role in it. At the same time, the focus of hormonal regulation shifts depending on the child's age:

• Basic provision: normal functioning of the thyroid gland and a sufficient level of thyroid hormones are critically important in all periods of life for adequate growth and proper cellular differentiation.
• Before the onset of puberty: the main stimulator of linear growth is somatotropic hormone (growth hormone, GH). It is secreted by the anterior pituitary gland.
• Pubertal period: sex hormones take on the leading role. It is they that ensure a sharp acceleration in growth rates (the so-called pubertal growth spurt). However, in parallel, sex hormones initiate the ossification of epiphyseal cartilages. This leads to the closure of growth plates and, as a consequence, to the final completion of human linear growth.

Class and exam questions

What else to study on this topic

• Mechanisms of development of diffuse and nodular goiter against the background of iodine deficiency
• Pathogenesis and clinical manifestations of iodine-deficiency hypothyroidism
• Physiology of somatotropic hormone (growth hormone) secretion by the anterior pituitary gland
• The process of epiphyseal cartilage ossification under the influence of sex hormones

Other topics in the section «Chapter 11. Endocrine Diseases in Children»

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