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Trace Elements and Electrolytes, Vol. ■■ – No. ■■/2013 (1-5)
Determination of serum zinc and magnesium levels in patients with hypothyroidism Original ©2013 Dustri-Verlag Dr. K. Feistle ISSN 0946-2104 DOI 10.5414/TEX01311 e-pub: ■■month, ■■day, ■■year
Key words hypothyroidism – zinc – magnesium – thyroid functions
Accepted for publication August 13, 2013 Correspondence to Muhamamd Ikram Ullah, ■■MD, Dr. Senior Teaching Research Fellow/ Health Professional Educationist, Department of Biochemistry, University of Health Sciences, Lahore, Pakistan ikram.uhs12@ gmail.com
Fakhar un Nisa1, Asim Mumtaz1, Muhammad Ikram Ullah2, Muhammed Atif1 and Waqas Sami3 1Department 3Department
of Allied Health Sciences, 2Department of Biochemistry, and of Biostatistics, University of Health Sciences, Lahore, Pakistan
Abstract. Objective: The objectives of this study were to determine the levels of Zinc and Magnesium in patients with hypothyroidism and to assess correlation of Zn and Mg with thyroid hormones. Subjects and methods: A total population of 50 patients of hypothyroidism and 25 normal healthy control subjects were included in this study. Total 10 ml of blood was collected for determination of free T4, free T3, TSH and trace element; Zn and Mg. Thyroid function tests were performed by the chemiluminescence method and trace elements were measured by atomic absorption spectrophotometer. Results: The age range of the patients and controls was 20 – 50 years. The mean age of the patients was 35.24 ± 6.79 years and mean age of the control subjects was 38.84 ± 6.68 years. No significant difference was observed for Zn in patients and controls. On the other hand, Mg was found statistically significant in patients and controls. There was a strong positive correlation between serum Mg and FT3, FT4 levels and a strong negative correlation between serum Mg and TSH levels. Conclusion: It was noted there was no alteration in Zinc rather than decreased levels of Magnesium in hypothyroidism patients. It might be suggested that serum Mg would be monitored in hypothyroidism patients to minimize the harmful effects of Mg deficiency in hypothyroidism patients. In the future, further studies should be conducted to demonstrate the exact involvement of these elements in disease mechanism.
Introduction Hypothyroidism is characterized by a generalized reduction in metabolic function that most often manifests as a slowing of physical and mental activity. The clinical presentation may vary from mild and asymptomatic to severe and overt disease and may also depend on the patient’s age, gender and physical condition. In most spontaneous •
cases, a decrease in thyroid function occurs gradually, with sub-clinical hypothyroidism progressing over time to overt hypothyroidism [1]. In hypothyroidism, levels of TSH in serum are raised while levels of Free T4 are decreased. Hypothyroidism is classified as primary or secondary. Hypothyroidism may present subclinically by the raised levels of serum TSH and normal Free T4 levels. It occurs more frequently in women; the overall incidence is ~ 3% of the general population [2]. Hypothyroidism presents with a wide range of clinical features, including fatigue, forgetfulness, moodiness, depression, hair loss, dry skin, puffy eyes, deepening of the voice, persistent dry throat, infertility and menstrual irregularities. Of particular concern, when it comes to heart disease, there is weight gain, elevated cholesterol and a slowed heartbeat [3]. In the metabolism of thyroid hormones various enzymes are responsible to catalyze the reactions. These enzymes required some essential trace elements including Zn and Mg for proper activity. Trace elements contributed very significant roles for biological processes. Deficiency or toxic levels of these elements may lead to improper functioning of the body. Zinc has important roles in thyroid metabolism [4]. It is involved in T3 binding to its nuclear receptor and participates in the formation and mechanism of action of TRH [5]. Thyroid hormone binding transcription factors also contain zinc bound to cysteine residues [6]. Zn is very important in thyrotropinreleasing hormone synthesis and is also essential for T4 to T3 conversion. It is required for the biological functioning of the thyroid
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hormones and related receptors. Zn deficiency has a suppressing effect on thyroid hormones, whereas zinc supplementation has an opposite effect [7]. Zinc is also crucial for proper thyroid hormone metabolism; zinc deficiency may result in decreased thyroid hormone levels and resting metabolic rate [8]. Tri-iodo-thyronine (T3) receptors, in common with other members of the nuclear receptor family, are thought to be included among the nuclear zinc-binding proteins [7]. Magnesium has been shown to activate adenyl cyclase in tissue homogenates and in isolated enzyme preparations. This divalent cation in vitro also stimulates cyclic 3,5 nucleotide phosphodiesterase. Since the action of thyrotropin on the thyroid gland is mediated by the formation of cyclic AMP, the availability of magnesium could affect the response of the gland to the pituitary hormone [9]. The objectives of this study were to determine the levels of Zn and Mg in patients with hypothyroidism and to assess correlation of Zn and Mg with thyroid hormones.
Materials and methods Prior to start of the study, ethical permission was obtained from the University of Health Sciences, Lahore, Pakistan.
Sample selection A total of 50 patients of hypothyroidism and 25 age and sex related healthy controls were included in the study. These patients were selected from the outpatient department of INMOL Hospital Lahore, Pakistan. The patients were comprised of individuals between 20 and 50 years of age and of either sex, mostly from low or middle income groups. Written consent was taken from the patients for inclusion in the study.
Sample collection The sample was withdrawn under aseptic conditions. A 6 ml blood sample was collected in EDTA vacutainer tube (BD vacutainer) for determination of Zn and Mg without venous stasis and without frothing. Plasma •
samples are preferred to serum for Zn analysis because of possible Zn contamination from erythrocytes, platelets and leukocytes during clotting and centrifugation. A 4 ml blood sample was collected in serum vacutatiner (BD Vacutainer SST II Advance tube) for determination of thyroid hormones. The samples were then centrifuged at 2,000 rpm for 10 minutes. Plasma and serum was separated and then carefully shifted into 1ml nitric acid treated aliquot. The aliquots were then stored at –20 °C till further analysis. Samples were neither lipemic nor hemolyzed.
Determination of thyroid hormones Thyroid function test including thyroid stimulating hormone (TSH), free thyroxin (FT4) and free tri-idothyronine (FT3) and was performed by chemiluminescence assay (VITROS ECiQ System). VITROS Immunodiagnostic Calibrators (REF 148 7289) were used to calibrate the instrument. Chemiluminescence is an immunometeric technique which is very sensitive and specific for hormone analysis.
Measurement of trace elements (Zn and Mg) Zinc and magnesium were measured on Atomic absorption spectrophotometer (ContrAA 700) which is a High Resolution Continuum source AAS (HR-CS AAS). It performs background correction simultaneously. It can measure elements up to part per billion (ppb) concentration with the graphite technique. It has an accuracy of 99.8% for Zn and Mg determination. Samples were digested with 10% nitric acid and incubated overnight in microwave temperature. Then samples were centrifuged to remove proteins and debris. The clear supernatant was used to dilute in nitric acid for analysis on atomic absorption. Zinc and Magnesium standards (1,000 mg/l, Merck) were used to generate calibration curves with different calculated concentrations of standards. After successful calibration of the instrument, quality control material with each batch of analysis was run to ensure that the results were reliable.
Data analysis
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Determination of serum zinc and magnesium levels in patients with hypothyroidism
Table 1. Comparison of Zn and Mg levels in patients and control subjects. Parameter Zinc Magnesium
Patient (Mean ± SD) 12.19 ± 3.33 0.683 ± 0.372
Control (Mean ± SD) 12.99 ± 2.70 1.01 ± 0.267
p-value 0.300
