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September 1991, Volume 41, Issue 9

Original Article


Khan Mohammad Sajid  ( Atomic Energy Medical Centre, Multan. )
Mehfooz Akhtar  ( Atomic Energy Medical Centre, Multan. )
Ghulam Qadir Malik  ( Department of community Medicine, Nishtar Medical College, Multan. )


A study comprising 41 males,5 females of the age ranging from 28 to 56 years was conducted during Ramadan of 1989 to compare T3, T4 and TSH levels in fasting with the levels of non-fasting conditions. Each individual gave 6 blood samples: One sample was taken 20 days before the onset of Ramadan, 3 samples at different fasting days and last two samples were drawn 23 days and five months after the end of Ramadan, respectively. The results showed a significant gradual rise in TSH throughout the fasting month, although the mean levels remained within normal limits. Pre- Ramadan levels were re-attained well after the end of Ramadan. There was no significant change in T3 and T4 levels(JPMA41: 213, 1991).


Fasting, one of Islamic essentials, is observed by most of the Muslims in the month of Ramadan. They awake in the last quarter of night, take their meals and stop food intake shortly before dawn. They do not eat or drink untill after the sun sets. Whereas documentation is available in fasting, starvation and malnutrited in­dividuals with known hormone economy, the short term, regular fasting is not thoroughly studied. Khan et.al3 in their study on 33 normal volunteers compared serum T3 and T4 levels during 15th hour of fasting with levels reached three hours after breaking the fast. They did not observe any significant difference. The biological and metabolic manipulations of thyroid hormones in the body, especially those related to slow metabolic rate and longer biologic half life of T4(about 7 days)2 suggests that such studies should also be conducted in conditions where the time gaps between fasting and non-fasting conditions are greater and the influence of number of days of fasting could also be recorded. We, therefore, conducted a study with changed sample schedules. TSFI estimations are also included in the study.


Normal subjects comprising 41 males and 5 females of ages ranging from 28 to 56 years, who fasted throughout the month of Ramadan(April-May’89) were included in the study. Males were mostly hospital staff whereas females were domestic women. The individuals fasted from 3:30 hours to 19:00 hours and had nothing by mouth during this period. Temperature in these days reached a maximum of 4 1°C. None of the subjects gave any history of thyroid illness or other disease. Each individual gave 6 blood samples. First sample was taken 20 days before the onset of Ramadan, 3 samples on 10th, 17th and 26th fasting days, and last two samples were drawn 23 days and five months (151 days) after the end of Ramadan, respectively. Ramadan samples were collected 15 minutes before breaking the fast. Pre and post Ramadan samples were taken at 13:00 hours. Meals during, before and after Ramadan were of average Pakistani composition. Proteins:12%(58g), Fat:6%(29g), Carbohydrate:82%(405g) and average caloric content was 2100 calories3. Activities of the individuals were restricted. Bed rest was also availed by 11 members.
Radioimmunoassay technique (double an­tibody) was applied to measure T3 and T4 levels, analyzing all samples in duplicate in single lots. TSH samples were measured by im­munoradiometeric assay. Intra-assay coefficients of variability were less than 6% within normal range of the hormones. Intra-assay drift calcu­lated using IAEA data reduction programme was less than 8% in all assays. The sensitivities of the assays were as follows:T3 RIA= 0.06 nmol/1, T4-RIA= 2.8 nmol/1, TSH-TRMA= 0.22 mU/i.
Students t-test of paired samples was used to compare variables. Results were expressed as X ± SEM, whereX=Mean and SEM= standard error of mean.


Non-fasting (pre-Ramadan & post-Ramadan) and DT4 fasting serum levels of T3, T4 and

TSH are shown in Table and displayed quantitatively in figures 1 and 2.

T3  and T4  values remained within normal limits and did not show significant changes throughout the study. The levels of TSH also remained within normal limils. However sig­TABLE. Mean (± SEM) Serum T3 , T4 nificant gradual increase in TSH levels was seen, which reached a maximum on 26th fasting day. The levels dropped after Ramadan but were stifi significantly higher than pre-Ramadan levels on 23rd day after the end of the month. The levels observed 5 months after the end of Ramadan were not significantly different from pre­Ramadan levels. Pre-Ramadan levels were probably re-attained at around two months after the end of Ramadan. The increased levels of TSH seem linearly related to the number of days of fasting.


Thyroid function is affected by age, non-specific illness, stress, some adrenal and gonadal hormones and many other miscellaneous states. Various nutritional states like diminished food intake, gross and total starvation also affect thyroid function in man, A number of studies have been published in this regard. Alexander reported in 1964 that total caloric deprivation results in decreased thyroid function4. Malnutrition or starvation in normal or obese subjects reduces plasma T3 During total starvation of 9 obese subjects for four weeks, mean plasma T3 was reduced in one study to about 50% of control values with some subjects reaching’ ‘hypothyroid level5. In another study comparable experimental con­ditions produced much smaller decrease in plasma T36. A study of chronic malnutrition in Indian adults shows reduction in plasma T3 to extremely low values (20% of normal:with refeeding T3 returns to or towards normal7). Study of Merimee on seven women and seven men who fasted for 60 hours, demonstrates that a decrease of circulating T3 is a constant feature of both men and women and that energy requirements are decreased by means of an altcration of circulating T3 concentration. This appears due to decrease in conversion of circulating T4 to T38, Conversion of T4 toT, is in liver and kidney (80% of daily T3 production arises from peripheral deiodina­tion of T49 is catalyzed by enzyme 5’- deiodinase. During fasting (or starvation), 5-deiodinase activity is reduced which results in decreased T3 production10. Work of Wartofsky and Burman11 (1982) shows that there is a 20% decrease in plasma T3 by the end of first day of fasting (24 hours) and a 50% decrease at the end of 3 days. With a prolonged fasting of more than 3 weeks T3 remains low. With refeeding original levels are restored. This happens due to decreased metabolic rates(and hence energy requirements)12. Decreased production ofT, is accom­panied by adaptive changes in the pattern of enzymes induced in the liver, so that T3 induction of a-glycerol­phosphate dehydrogenase is maintained but T3 induc­tion of malic enzyme is not13. Reported results on plasma T4 are variable: T4 is unaffected or decreased during caloric deprivation5,6. TSH results in short term and long term fasting are also variable. In normal adults basal levels ofTSH decreased by 50% after 36 hours of fasting” but levels were unaffected in chronic malnutrition in adults7,14,15 and children16. During total starvation of obese subjects for several weeks, basal TSH concentra­tions were unchanged or slightly decreased5,6. It is also shown by others17 that serum TSH levels may be normal or slightly elevated under some conditions of non­thyroidal illness including hepatic cirrhosis, starvation etc. but without apparent correlation with either T3 or T4 concentrations. Recently a 5 years old boy who was under malnutrition due to dietary maladvice for 3 years developed iodine deficiency hypothyroidism with low Ti and high TSH levels18. Decrease in T3 levels during fasting could also be attributed to greater metabolic clearance and biologic activity of T, relative to Ti. The values of T4 in our subjects seem decreasing (as shown in Figure. 1) with number of days of fasting, although this decrease is not significant on statistical analysis.
Ramadan fasting which is expanded over a fraction of day is observed daily for one month. The literature is almost silent as regards this type of fasting. The findings related to malnutrition and starvation in literature show a constant feature of human population over a period of months or years. Fasting is confined to nutrient lack. Ramadan fasting (or short term regular starvation type fasting) is a single incidence for a duration extending over days or weeks. Such fasting is therefore different. The periodic daily fasting requires the thyroid to adjust its function gradually to the new menu. The thyroid profile will behave in a different mode. In the reported situations T3 levels are reduced but the extent of decrease is different in different situations. T4 and TSFI levels may change or remain unchanged. In Ramadan there is no food deprivation(except for a limited interval daily), T3 levels are, therefore, not lowered as may be expected (peripheral conversion of Ti to T3 compensates small variations in T3 levels). Ramadan fasting reflects a gradual decrease in Ti levels which is not significant in a month interval (Figure 1). This decrease is visible only if pre-Ramadan sample is taken as control. However, TSH estimates in our study showed a significant gradual rise (within normal limits) which reached a maximum at the end of the month (Figure.2). Is this rise related to the reduction in T4 levels or has it to do with dietary changes? This requires further thorough investigation.
Synthesis and secretion of thyroid hormones depend upon the individual rates of several enzymatic conversions from tyrosine to Ti. Deficiency of one or more of these enzymes could block the synthesis of Ti (e.g., in hypothyroidism)19. Increased thyroid stimula­tion could improve the synthesis. The possibility is notyet explored. Perhaps the enzymatic activities are affected by fasting. Wider trial experiments are, therefore, required for worth exploration.
Our study is interesting in the sense that the samples were repeated at fixed intervals of time and comparisons were made with pre-Ramadan samples of same individuals.


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