Lead poisoning secondary to hyperthyroidism: report of two cases

Abstract

With long-term exposure to lead, lead accumulates in bone, where it is stored for years. These quiescent lead stores are mobilised when increased bone turnover occurs, and latent lead toxicity may then become symptomatic. Although Graves' disease is a common cause of increased bone turnover, to date hyperthyroidism has been implicated in lead poisoning only twice. We describe herein two cases of hyperthyroidism, one caused by toxic multinodular thyroid enlargement, the second by Graves' disease, leading to lead poisoning. Treatment of hyperthyroidism with radioactive iodine cured both hyperthyroidism and lead poisoning and no chelating agent therapy was necessary. Lead poisoning is an important environmental health problem, and physicians must be aware of the endocrine disorders such as hyperthyroidism and hyperparathyroidism that increase bone turnover, favouring lead mobilisation. Atypical symptoms should draw the physician's attention to the possibility of lead poisoning, particularly in workers with occupational exposure to lead and in areas where lead poisoning is endemic.

Effects of lead on thyroid functions in lead-exposed workers

“…Once absorbed, lead accumulates in three compartments: blood, soft tissues and especially in bones, where it can be stored for years [11]. Factors that affect calcium distribution also affect lead distribution [6]. The lead circulating in the bloodstream is mobile, in contrast to that stored in bones and it is this lead that exerts adverse effects on the body [7].…”

“…For this reason, the concentration of lead in the blood is an important parameter in the characterization of a person's exposure to lead [7]. Lead can cause hematological, gastrointestinal, rheumatological, endocrine, neurological and renal problems in humans [6][7][8]11].…”

“…Occupational and environmental exposures to lead continue to be among the most significant public health problems [1][2][3]. Lead can have adverse effects on many organ systems, and various effects of lead on thyroid functions have been reported in the past 50 years [4][5][6][7][8]. However, findings have been inconsistent and sometimes contradictory, and no consensus has been reached regarding the effect of lead on thyroid physiology.…”

A review on paediatric lead toxicity

“…Concentrations of lead in umbilical cord blood were found to be 80-100% of the maternal blood lead level [2,17,18]. Several conditions known to increase bone turnover, such as pregnancy, lactation, chemotherapy, tumour infiltration of the bone, or postmenopausal osteoporosis, may be associated with the mobilization of lead in bone stores, leading to chronic lead toxicity [18][19][20][21]. Although hyperthyroidism also increases bone turnover, it has only rarely been implicated in the pathogenesis of lead poisoning, with only two reported cases [19].…”

Noninvasive Determine Lead Poisoning Biomarker for Human Body—Design and Manufacture on Innovated New-XRF Analyzer of Bone Lead

“…The bone lead can even make the teenager increase nerve behavior, commit crime, offensive behavior. To the pregnancy and the breast feed women under inside or outside hormone effect can result in the bone lead in great quantities to mobilize to the whole body, making poisoning symptom to be increased [2]. This situation only relate to bone lead, nothing to do with blood lead .It is thus clear that we should increase the bone lead content marker [3].…”