INTRODUCTION:

Alkaline phosphatase (ALP) is a membrane‑bound glycoprotein found on most cell membranes in the body and physiologically occurs during bone formation in developmental stages (1,2). ALPs are a group of enzymes found primarily in the liver and bone. There are small amounts produced by cells lining the intestines, the placenta, and the kidney, also they concentrated in mature or immature leukocytes, as neutrophil ALP (NAP) (3).

What is measured in the blood is the total amount of ALPs released from these tissues into the blood.

As the name suggests, this enzyme works best at an alkaline pH, and thus the enzyme itself is inactive in the blood (4). Serum ALP levels are reported to be abnormal in thyroid disorders (5).

Hypothyroidism retards formation and destruction of bone. Hypothyroidism for more than a year will lead to retardation of bone age (6). Adult hypothyroid patients tend to exhibit higher than normal bone density. It is usually associated with normal or low ALP together with normal serum calcium and phosphorus concentrations (7). Periodontitis, common infectious diseases in humans, are characterized by gingival inflammation and a loss of connective tissue and bone around the roots of teeth, which leads to eventual tooth exfoliation. In the past decade, the association between this disease and the development of systemic diseases has received increasing attention (8). Hypothyroidism has been considered as one of the causes of periodontal disease (9). Bacteria present in the sulcus or pocket also produce ALP and contribute to ALP levels in saliva. ALP in saliva has been suggested as a potential diagnostic marker for periodontitis (10,11). Their increased activities might be a consequence of destructive processes in alveolar bone in advanced stages of development of periodontitis (12). Therefore this study was established to measure the level of ALP in serum and saliva of hypothyroid patients with and without periodontitis.

SUBJECTS AND METHODS:

This study was carried out on 60 (4 males and 56 females) Iraqi hypothyroid patients their ages ranged (20- 64) years (as total patients), were rounded up from Nuclear Medicine and Radiation Therapy Department, Educational Oncology Hospital. 30 of them were diagnosed with periodontitis. The diagnosis was made through specialized dentists in the department of Periodontics, College of Dentistry- Baghdad University. Besides 30 (3 males and 27 females) volunteers subjects, considered as control, their ages and gender were matched with patients; their ages ranged between (20-55) years. Serum and saliva samples were collected from study groups.

Approximately (4 ml) of human blood was collected intravenously from patient and control groups; also, unstimulated saliva (3 ml) was collected from studies groups. Both of them centrifuged at 3000 rpm for 10 minutes. Serum of blood was immediately separated, and the supernatant of saliva aspirated immediately, both divided into aliquots and kept at (-20 °C) until used. The diagnosis of hypothyroidism was based on the clinical features and biochemical tests that depended mainly on elevated serum levels of TSH, low T₄ level, and low or normal T₃. All patients had no complained of other chronic or systemic diseases, and pregnant women were excluded from the study. Detection of ALP level in serum and saliva were determined by using commercially available Alkaline Phosphatase -liquicolor (Human com., Germany).

The Statistical Analysis System- SAS (2012) program was used to identify the effect of different factors in study parameters. The quantitative outcome variables were normally distributed, and therefore conveniently described by mean, standard error (SE) and tested for statistical significance by t-test and ANOVA test.

RESULTS AND DISCUSSION:

The results presented in the present study are based on the analysis of 60 hypothyroidism patients (30 patients with periodontitis and 30 patients without periodontitis) compared with 30 individuals as controls. The age of hypothyroidism patients ranged between (20-64) years with a mean age of (39.88 ± 1.423) years. However, the majority (43.33%) of patients are in the age group of (35-45) years. Furthermore, there is a significant female's predominance among patients group. Males/females ratio is (1:14), and no statistically significant differences (p>0.05) in age or gender existed between patient and control groups.

The results of this study revealed that serum TSH levels are significantly higher (P<0.001) in hypothyroid patients (10.26±0.36 μIU/ml) as compared to control group (5.99±0.25 μIU/ml). On the other hand, serum levels in patients group of tT₄, fT₄, tT₃ and fT₃ (3.54± 0.17 μg/dl, 0.891±0.04 μg/dl, 0.572±0.02 ng/dl, and 1.227±0.06 pg/ml) are significantly low (P<0.001) as compared to levels in control group for tT₄, fT₄, tT₃ and fT₃ (6.12±0.37 μg/dl, 1.489±0.08 μg/dl, 0.813±0.04 ng/dl and 2.206±0.16 pg/ml) respectively, these results illustrated in the table (1).These results confirmed the diagnosis of hypothyroidism which is characterized by elevated TSH and declined T₄ and T₃ hormone levels compared with levels in control.

The results of serum thyroid hormones levels are in accordance with the observations of the previous researchers, Senthilkumaran et al. 2015 (13) and Hasan et al. 2016 (14), who demonstrated that hypothyroidism patients have elevated serum level of TSH and decrease levels of T₄ and T₃ than that in controls. Consistency, Li et al. 2014 (15) revealed that there are significant differences between controls and hypothyroid patients in levels of tT₄, fT₄, tT₃, fT₃ and TSH. On the other hand, Jayan and colleagues, 2015 (16) suggested that elevation in serum TSH is an early and sensitive indicator of decreased thyroid reserve and in conjunction with decreased fT₄ and ft₃ is diagnostic of primary overt hypothyroidism.

It is well known that patients with low thyroid hormone levels have increased TSH levels because of the negative feedback relationship between the different hormones. The majority of hypothyroidism cases result from primary thyroid failure. Consequently, pituitary gland responds to that failure by secreting more TSH, raising serum TSH levels fairly before there is a detectable decline in circulating thyroid hormones T₄ and T_3, afterward, the levels of fT₄ and fT₃ reduced (17).

The current results in table (2) revealed that serum ALP levels are significantly low (P<0.001) in hypoythyroid patients group and hypothyroid patients with periodontitis group (8.57±0.76 and 7.04±0.69 U/I) respectively, as compared to control group (19.01±2.16 U/I), and there are non-significant differences (P>0.05) between the level in hypoythyroid patients group (8.57± 0.76 U/I) and hypothyroid patients with periodontitis group (7.04±0.69 U/I).

Regarding salivary ALP levels, this study demonstrated that mean levels in group of hypothyroid patients with periodontitis (9.61±0.61 U/I) are increased significantly (P<0.001) as compared to group of patients without periodontitis (5.85±0.47) and control group (4.78±0.26 U/I), and there are no significant differences (P>0.05) between the salivary levels in group of hypothyroid patiets (5.85±0.47 U/I) and ontrol group (4.78±0.26 U/I).

Table (2): Serum and salivary ALP level in study groups

Hormones

(Mean ± SE)

Serum ALP

(U/I)

Salivary ALP

(U/I)

Hypothyroidism

(N=30)

8.57 ± 0.76

5.85 ± 0.47

Hypo. with Periodontitis

(N=30)

7.04 ± 0.69

9.61 ± 0.61

Control

(N=30)

19.01 ± 2.16

4.78 ± 0.26

LSD

3.925

1.499

ANOVA (P value)

P<0.001**

A, B: Different letters in the same column represent significant differences.

SE: Standard Error; **: Highly Significant (P<0.001).

The declining level of serum ALP among hypothyroid patients in the current study agrees with the finding of Mane and Bhagwat in 20011 (18) and Mane and Bhagwat in 2012 (19) who mentioned that ALP values in hypothyroid were significantly lower compared to control. Also, in 2009 Mane (7) indicate that adult hypothyroid patients associated with normal or low ALP together with normal serum calcium and phosphorus concentrations, tend to exhibit bone density higher than normal. While, Arora et al. 2009 (20) found that no significant difference in ALP level when compared all subjects in the hypothyroid group with euthyroid subjects, which may be due to the presence of some cases of sub-clinical hypothyroidism in this group. Another study done by Pandey et al. 2013 (21) showed raised serum ALP level considerably in hypothyroidism. The decrease in serum ALP level among hypothyroid patients may be related to low serum concentration of magnesium and zinc in this condition, subsequently restoring serum magnesium and zinc to normal levels also restored the serum ALP activity to normal; or it may be related to decreased production of ALP by osteoblast, which required thyroid hormones (22,18).

The function of thyroid hormones are known to affect bone turnover, whereas bone turnover in hypothyroidism is decreased in favor of resorption and the rate of resorption is associated with the levels of thyroid hormones in hypothyroidism; besides ALP is also distributed predominantly in bone tissue (18). In addition to above, most markers of bone turnover are decreased in patients; all these factors together confirm that the changes in ALP are not due to an abnormality in liver function, it is more likely due to altered bone metabolism (23, 24). There is evidence that T₃ acts to stimulate bone ALP (B-ALP) activity through an osteoblast nuclear receptor-mediated process. B-ALP comprises approximately 50% of total circulating ALP in normal subjects (25).

In spite of there is no significant difference in serum ALP level between two patients groups (with and without periodontitis), but the level in group of patients with periodontitis still lower than the level in group of patients without periodontitis. This difference could be due to the effect of periodontitis because many studies reported a significant decrease in serum ALP level in periodontics patients (26,27). Decrease ALP level among periodontitis patient could be correlated to increased bone destruction with reduced apposition of bone (27). Otherwise, this decrease might be attributed to very less bone apposition nature during the active phase of the disease and or may be related to the severity of disease leading to increased bone destruction with a reduction in bone formation (28).

About the result of salivary ALP levels in hypothyroidism patients, there are no other studies to compare this result with it.

However, the significant increase of salivary ALP levels in group of hypothyroidism patients with periodontitis might be a consequence of destructive processes in alveolar bone and metabolic changes in the inflamed gingiva. ALP increased significantly with increased inflammation and plaque accumulation indicates a higher level of cellular damage (29,30).

While ALP in serum has been associated with bone disease, local elevations in saliva could reflect local hard and soft tissue alterations in active periodontal disease; the presence of ALP in the saliva is usually indicative of inflammation and/or destruction of the periodontal tissues (31). ALP is stored in specific granules and secretory vesicles of neutrophils and is mainly released during their migration to the site of infection (10). There is neutrophil predominance in the pocket epithelium, and the major source of ALP during inflammation has been proposed to be neutrophils. This postulate is further strengthened by the results of the plaque, which suggested that bacterial ALP contributed <20% to total ALP activity in saliva (32).

In conclusion the present study provides evidence that activity of ALP is dropped significantly in serum indicate that bone resorption occurs at a lower rate as a result of decline thyroid hormones, which can affect oral health, concluded alveolar bone and periodontal tissue destruction indirectly

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Received on 04.10.2017 Modified on 26.11.2017

Research J. Pharm. and Tech 2018; 11(7): 2993-2996.

DOI: 10.5958/0974-360X.2018.00551.6

Hormones in serum (Mean ± SE)	TSH (μIU/ml)	tT₄(μg/dl)	fT₄(μg/dl)	tT₃(ng/ml)	fT₃(pg/ml)
Total patients (N=60)	10.26 ±0.36	3.54 ± 0.17	0.891 ± 0.04	0.572 ± 0.02	1.227 ± 0.06
Control (N=30)	5.99 ± 0.25	6.12 ± 0.37	1.489 ± 0.08	0.813±0.04	2.206 ± 0.16
t-test (P value)	P<0.001**	P<0.001**	P<0.001**	P<0.001**	P<0.001**