The Gerson Institute of Ayurvedic Medicine

Scott Gerson, M.D., Ph.D. (Ayurveda) Medical Director, Jupiter Medical Center Dept. of Integrative Medicine Division of Education and Research

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Jatharagni, Dhatvagni, and the Thyroid Gland

The Sanskrit word agni (root ag, to move tortuously), in common language, means fire. In the Western schools of Ayurveda it is commonly understood as “digestive fire” implying its correlation with the various digestive juices of the stomach, small intestines and related exocrine glands. It is commonly understood that agni maintains the integrity of the body by converting consumed foods, via pakadi karmas or bio-chemical processes, into cellular organelles and body structures, However, when the sages of Ayurveda speak of agni with respect to a living organism, it has a much broader significance. Foods are not only converted into various physical structural and functional constituents but also into the biological energy necessary for the myriad of mental, emotional and other vital human activities. Consider what Sushruta tells us in his ancient writings:

जाठरो भगवानग्ननरीश्वरोऽन्नस्य ऩाचक् | सौक्ष्म्याद्रसानाददानो वववेक्तुं नैव शकय्े ||२७||

“The fire burning within the individual is divine in its subtle essence and divine attributes of atom-like invisibility, weightlessness, as well as digesting all foods.” (SS Su 35:26 )

Thus, it is clear that this term, agni, connotes something far more comprehensive than “fire”. Agni represents the divine essence or celestial fire present in every atom of the universe.

The Charaka Samhita states that “agni is responsible for life span, complexion, strength, health, enthusiasm, corpulence, luster, immunity, energy, heat processes and prana. One dies if agni is extinguished, lives long free from disease if it functions properly, and suffers illness if it becomes deranged. Agni is the root cause of health, disease and life.” (CS, Chi.15/3-4).

As is true with many concepts in Ayurveda which have been superficially understood in the West, the true significance of agni is simplified and distorted in translation. The first part of this article, will clarify the true significance of the term agni which encompasses the many processes which regulate and direct the processes of macro (intestinal) and micro (cellular) digestion but perhaps more significantly manages the general metabolism of the entire human organism. The second part proposes a possible connection between dhatvagni and the thyroid gland.
The Ayurvedic subspecialty known as kayachikitsa is often (mistakenly) translated as “internal medicine”. However the term kaya specifically denotes the entire assemblage (kaya=body, trunk; assemblage) of underlying metabolic life processes and so kayachikitsa (chikitsa = treatment) is more properly defined as the treatment of diseases which arise as a result of metabolic disturbances. The true scope of the term agni is suggested when we consider that kayachikitsa is actually also defined as the treatment of the antaragni or agni located deep within the interior.

Agnishastra: What is Typically Taught

Let us first review the most common usage of the term agni in Western Ayurvedic parlance. In its most mundane sense of “digestive fire”, agni is conceptualized to heat and break down our food and render it appropriate for absorption into the body. We all know from basic chemistry
that heat causes the separation, breakdown, and disintegration of any substance into its simplest components. Heat also is known to catalyze and accelerate various types of chemical reactions.

Similarly, the macro-digestion of food in the stomach (āmāśaya) and small intestine (pakvāśaya) involves the splitting of complex, difficult to absorb food substances into their simpler components. Specifically, the digestive machinery performs the breakdown of:
 complex proteins into single amino-acids
 fats into individual fatty acids and glycerol, and
 complex sugars and starches into glucose, fructose and other simple sugars

All of these simpler breakdown products can be easily absorbed. All of this is made possible by jatharāgni. We must add here that there are several classifications and synonyms for agni each of which emphasize different aspects or functions.
Charaka describes thirteen individual agnis categorized into three types of based on function.

1. Jatarāgni (1) regulates the digestion of ingested food and general metabolism.
2. Bhutāgni (5) regulates the conversion of the five gross elements in ahara rasa (liquified intestinal food juice) into a more subtle form for incorporation into the bodily tissues by the dhatvāgni.
3. Dhatvāgni (7) regulates the sequential conversion of simpler tissues into the next more complex one e.g. the conversion of rasa into rakta, rakta into mamsa etc. Of these 13 types of agni, jatarāgni is most important and master of all agnis. It is jatarāgni which has relevance to the global metabolism of the human being and thus is the one we are concerned with here. Synonyms for it include antaragni, kayagni, pachakagni, and pachaka pitta.

There are four functional states of jatarāgni according to the dosha or doshas which may have the greatest influence. They are:
(1) Mandagni due to the influence, predominantly, of kapha
(2) Tikshnagni due to the influence, predominantly, of pitta
(3) Vishamagni due to the influence, predominantly of vata and
(4) Samagni due to the influence of the normally balanced doshas,

Mandagni: This is a state in which the action of jatharagni is considerably inhibited due to the dominant influence of kapha. In this state, the agni is unable to digest and metabolize even a small quantity of otherwise even easily digestible food. There can be associated edema, heaviness of the limbs and loose bowel movements.

Tikshnagni: The jatharagni, in this condition, is said to be excessively excited. Tikshnagni easily digests even a very heavy meal, in a very short space of time. It causes ravenous hunger - a condition sometimes called atyagni (or bhasmaka in later texts). A person with tikshnagni can
(unfortunately) digest his all too frequent meals. Because it is related to pitta dosha, it can produce parched throat, palate and lips, bodily heat, rashes and other pitta signs.

Vishamagni: A changeable and erratic state of the agni arises as a result of the influence of vata dosha and is known as vishamagni. In this state, the action of agni is irregular and sporadic. It sometimes results in complete digestion and at other times produces vata manifestations such as abdominal distension, colicky pain, constipation. If allowed to persist, vishamagni can become a contributing factor in causing various kinds of vataja, pittaja or kaphaja diseases.

Samagni: In the balanced state of the functioning tridoshas, the jatharagni is also found to be balanced and to function normally. The jatharagni effortlessly digests and assimilates ingested food in a normal time frame without any kind of distress.

Beyond the Gut

As described above then, the jatharāgni is mainly concerned with the processes involved in gastrointestinal digestion. There are, however, two aspects to jatharāgni viz., (a) local and (b) systemic. The local relates to factors which are directly related to the digestion of food materials in the āmāśaya and pakvāśaya, corresponding to the gastric and intestinal digestion.
The systemic aspect relates to the Ayurvedic understanding that the jatharāgni contributes to the creation and maintenance of the five bhutagnis and the seven dhatvagnis. In other words, the systemic aspect of agni is its effect on cellular and tissue metabolism, which raises the main question of this article: Does the jatharāgni—located in the distal stomach and proximal duodenum—have distant effects on every kind of cell and tissue throughout the body? It would seem that this is precisely what Ayurvedic shastra is telling us. But how is this possible and is there a modern medical or anatomical explanation of a possible mechanism? What makes the question more intriguing is that the seven bodily tissues (i.e. blood, blood cells, muscle, fat, bone, marrow, etc.) are not generally located in only one organ or area but are spread out throughout the body.

We know for certain that there are no nerve fiber connections between the stomach-duodenum (āmāśaya-grahani) region and the seven bodily tissues. However we have known for some time that there are many hormonal substances secreted from the stomach and duodenum and widely distributed which have important physiological effects. Most of these documented effects are local in nature and have actions limited to other regions of the digestive system. For example, the effect of the duodenal hormone secretin is to promote the secretion of pancreatic juice; also fat entering the stomach stimulates the mucosal cells of the duodenum (grahani) to secrete the hormone cholecystokinin which in turn stimulates the gallbladder to secrete bile.

Several other intestinal hormones and chemicals, elaborated by the duodenal mucosal glands, such as gastrin, GIP, motilin, enterogasterone support different aspects of digestion through regional effects. However, Ayurvedic writings seem to indicate the existence of factors, most likely hormonal secretions, which help regulate--either directly or indirectly--tissue-metabolism, outside of the digestive system and in fact systemically in tissues throughout the body.

There are other possible mechanisms by which subtle connections could exist between seemingly distant and diverse aspects of the human physiology. Consider the peculiar human embryonic cell structure known as the “neural crest” which forms from the primitive ectoderm layer sixteen days after fertilization. At this stage the human embryo is 0.4 mm long (<⅛ inch). Neural crest cells are a transient, pluripotent, and—most importantly—migratory cell population unique to vertebrates that gives rise to a diverse cell lineage including melanocytes, craniofacial cartilage and bone, smooth muscle, thyroid, thymus, adrenomedullary, carotid, cardiac, cranial nerves (V, VII, IX, X), peripheral and enteric neurons and glia.

Now according to recent insights from a quantum mechanical concept known as entanglement, any two objects (say two electrons or two neural crest cells) that have ever interacted are then forevermore connected and “entangled”. In other words, what happens in one object instantaneously affects the other object despite the lack of any physical connection between them. This has been proven without a doubt. Quantum mechanics is revealing very strange things about life and reality—things that we do not understand and even disturb us. For instance, entanglement exists even if the interaction is due to both objects never interacting with each other but rather with a common third object. In essence quantum mechanics is telling us not only that all cells and tissues in our bodies are connected but that we are living in a world of universal connectedness. Thus all of the tissues which originated in the neural crest—including thyroid tissue—could remain “entangled” despite their eventual migration to distant areas.

Figure1. Relationship of primordial endodermal thyroid cells to the mesoderm

Here is another example. The figures above are schematic illustrations of germ layer interactions during formation of the primitive gut tube of the human embryo at approximately 2 weeks. (A) The endoderm (green) is in close proximity to the lateral plate/cardiogenic mesoderm (purple), providing an anatomical foundation for cross-signalling between cell populations (boxed region; see B). The spatial relationship in early development between the endoderm destined to a thyroid fate and lateral plate mesoderm/cardiac mesoderm has not yet been clearly defined. (B) Mesodermal cells may in some way elaborate signals of as yet unknown nature that affect the morphogenesis in the adjacent ventrolateral endoderm. Moreover, signalling in the opposite direction (i.e. from endoderm to mesoderm) also occurs. The endoderm in this location contains cells in which thyroid progenitor cells are specified before entering the thyroid placode in the pharyngeal floor not yet formed. (C) After the gut tube is closed, the thyroid placode is located in the midline of the pharyngeal endoderm directly adjacent to the developing heart.

Systemic influence of Jatharāgni

As regards the general or systemic influence alleged to be exercised by jatharāgni through dhatvagni on general metabolism, we note several relevant observations contained in the Ashtanga Hridaya and the Charaka Samhita.
"Fractions of kayagni (jatharāgni), established in its own place (the stomach), are distributed to and permeate all the dhatus. A decrease of it (below the normal) allows for an increase of the dhatus, while an increase of it (above the normal) makes for a decrease of the dhatus." (AH Su. 11:34).

This sloka poses an apparent paradox because it states that an increase in dhatvagni causes a decrease in that respective dhatu. This can perhaps be clarified by considering the clinical presentation of the condition spoken of as atyagni described by Charaka (and other authorities) which bears a striking resemblance to the symptomatology of the hypermetabolic state sometimes associated with the hypo- or hyperactivity of the thyroid gland. Says Charaka,

"In a person, in whom kapha undergoes decrease and pitta becomes excited, aided by vata the excited pitta extends to the pachakasthana where, it augments pachakagni into hyperactivity. The pachakagni thus augmented, together with vata in the body, which latter has been rendered very dry rapidly and with frequency digests the food ingested on account of its intensity, as soon as the food is eaten. Having thus consumed the available food, it (agni) begins to consume the sharira dhatus, such as rakta etc. The person is then afflicted with extreme asthenia and diseases, leading ultimately to death. His hunger for food appears to be relieved when food is taken, but, he soon after feels faint and restless and develops thirst, dyspnea, burning and other disorders of excessive fire.” (CS Chi. 15:217-221 )

सप््भभदेहधा्ारो धा्वो द्ववववधुं ऩतन् | यथास्वमग्ननभभ् ऩाकुं याग्न्् ककट्टप्रसादव्् || (१५:१५)

Sapta bhirdeha dhātāro dhātavo dvividham punaḥ | yathā svamagnibhiḥ pākam yānti kitta prasādavat||

“The dhatus supporting the body are ultimately converted (metabolized) by one of the seven corresponding agnis into one of two substances essence or waste.” (CS Chi. 15:15) (Also see AH Sa 3:49-51)

Two important points emerge out of these references. (i ) pachakagni, located in its own place between the pakvāśaya and āmāśaya, contributes parts of itself to the dhatus and, ( ii ) the moieties of pachakagni present in the dhatus, when excessive/hyperactive, leads to their atrophy or if hypoactive, to their hypertrophy.

These points may be (cautiously) illustrated by considering the hyper- and hypo-metabolism associated with the modern conditions of hyper- and hypothyroidism. It is, however, important to note that exact correlations between modern diseases and Ayurvedic diseases are rare. With this caution in mind, it is interesting to compare the striking parallels of thyroid hormone to the concept of the jatharāgni reaching and functioning in the dhatus as dhatvagni.

Galaganda

To be precise, there is nowhere any direct mention of thyroid gland in any classical Ayurvedic writings until the twentieth century. But a disease by the name galaganda is mentioned in the samhitas of the Vedic Period. The earliest description of neck swelling is actually found in the Atharva Veda (c.1000 BC) by the name apachi. Charaka first described galaganda as one of the twenty varieties of sleshma vikaras. Susruta states that out of the seven layers of skin, the sixth layer--Rohini--is galaganda rogadhistana (Su.Sa.4/4). In Nidanasthana he described galaganda as two encapsulated swellings in the anterior angle of the neck, which hang like a scrotum (Su.Ni.11), whereas Charaka described galaganda as a solitary swelling. (Ch.Ch.11). The Kashyapa samhitakara added that parts of the country which are cold, damp, with densely grown tall trees, water stagnation and heavy rains may support development of galaganda.

From the above descriptions one can see how galaganda can be correlated with goiter or some other pathology, where thyroid function may or may not be affected. But hypothyroidism is not just a localized disease. It has many symptoms related to many systems of the body. So from the scant descriptive and etiological information left to us in the samhitas, it is not possible to extrapolate hypothyroidism from galaganda.
According to more modern Ayurvedic teachings, the thyroid gland belongs to Majja dhatu (bone marrow). The brain is considered Majja dhatu as it too is a soft tissue encased in bone. Majja is dominated by Kapha dosha. The colloidal contents of the thyroid follicles certainly reflects this dosha as does its embryological origins in the endodermal germ layer. (Its parafollicular cells which make calcitonin actually derive from ectoderm.)
Observing the general characteristics of thyroid function we can easily see Pitta dosha as the dominant force. Pitta is responsible for all of the metabolic actions carried out by the thyroid gland. The principle function of thyroid hormone is to act as a catalyst, a kind of 'spark', for the maintenance of oxidative metabolism in most tissues. Stated in another way, the principal function of thyroid gland is to regulate the rate of cellular metabolism. The amount of input the cells receive from thyroid hormone will determine how briskly they perform their functions.

Effects of Thyroid Hormone

We know thyroid hormone certainly exercises profound influence on tissue metabolism throughout the body. Abnormalities in the secretion of this hormone have been shown to be responsible for engendering far-reaching metabolic effects.
Thyroid hormone, as is well known, normally activates cellular oxidative processes throughout the body. The exact mechanism by which it acts is not fully understood.

We do know that receptors for thyroid hormones are intranuclear DNA-binding proteins that function as hormone-responsive transcription factors, very similar conceptually to the receptors for steroid hormones.

Thyroid hormones enter cells through membrane transporter proteins. Once inside the nucleus, the hormone binds its receptor, and the hormone-receptor complex interacts with specific sequences of DNA which act as promoters of responsive genes. The effect of the hormone-receptor complex binding to DNA is to modulate gene expression, either by stimulating or inhibiting transcription of specific genes.
Excessive thyroid hormone induces a significant rise in basal oxygen consumption by tissues or hyper-metabolism. The condition described as atyagni (lit. “excessive agni”) is also known as bhasmaka. The word bhasmaka literally means “to reduce to ashes” or “to burn”. On the other hand, an insufficiency of this hormone is followed by a reduction in the oxidative reaction. While it is, however, necessary to guard ourselves against confusing or mixing up hypo-metabolism with hypo-thyroidism, thyroid hormone is known to act as a catalyst to both maintain and increase the oxidative processes in the many tissues.

It is in fact likely that all cells in the body are targets for thyroid hormones. A few of the more important effects of thyroid hormone are discussed briefly below.

Metabolism: Thyroid hormones stimulate diverse metabolic activities in most tissues, leading to an increase in basal metabolic rate. One consequence of this activity is to increase body heat production, which is related to increased oxygen consumption and rates of ATP hydrolysis. The relation of thyroid hormone to agni is that of wind blowing on the embers of a fire.

 Lipid metabolism: Increased thyroid hormone levels stimulate fat mobilization, which increases concentrations of plasma fatty acids in. Furthermore, they also stimulate fatty acid oxidation in many tissues. Plasma concentrations of cholesterol and triglycerides are inversely correlated with thyroid hormone levels, making increased blood cholesterol concentration a useful diagnostic sign of hypothyroidism.

 Carbohydrate metabolism: Thyroid hormones stimulate almost all stages of carbohydrate metabolism, including amplification of insulin-dependent entry of glucose into cells and increased gluconeogenesis and glycogenolysis to generate free glucose. It also increases excretion of nitrogen and calcium. The individual feels hot all the time and, despite ravenous food consumption, body weight may decrease.

Growth and Development: Thyroid hormones, together with growth hormone, are clearly necessary for normal growth in children and young animals, as evidenced by the growth-retardation observed in thyroid deficiency. A classical experiment shows how tadpoles deprived of thyroid hormone fail to undergo development into frogs. Of critical importance in mammals is the fact that normal levels of thyroid hormone are essential to the development of the fetal and neonatal brain. Deficits in of memory, intellect and thought, , dry rough skin, thin brittle hair, hair fall, Muscle stiffness, aching, myalgias, cramps, weakness and fatigue, myxedema, constipation, and hoarseness of the voice.

Cardiovascular system: Thyroid hormones increase heart rate, cardiac contractility and cardiac output. They also promote vasodilation, which leads to enhanced blood flow to many organs. Hypothyroidism can produce cold intolerance and hypotension.
Central nervous system: Both decreased and increased concentrations of thyroid hormones lead to alterations in mental state. Too little thyroid hormone, and the individual tends to feel mentally sluggish, while too much induces anxiety and nervousness.

Reproductive system: Normal reproductive behavior and physiology is dependent on having essentially normal levels of thyroid hormone. Hypothyroidism in particular is commonly associated with menstrual irregularities, infertility and loss of sex-drive.

As pointed out earlier, it is not sought here to identify thyroid hormone with the small moieties of jatharāgni stated to be contributed to the dhatus. Nonetheless, the possibility of some factor or a complex of factors--possibly hormonal--located in the duodenum which may exercise a regulatory influence on the thyrotrophic functions of the anterior pituitary gland, can be visualized. This idea is consistent with the continuing discovery of various hormonal substances in the duodenal mucosa; the possibility of perhaps another hormone which could have thyroid-regulating actions is certainly not farfetched. Or perhaps hitherto unknown activities of known intestinal hormones may come to light. One example is vasoactive intestinal peptide (VIP), whose main actions are to relax the lower esophageal sphincter, stimulate secretion of water into pancreatic juice and bile, stimulate secretion of water and electrolytes, and to dilate peripheral blood vessels. It has been found that this “intestinal” peptide has far-reaching extra-intestinal actions including the stimulation of the heart and thyroid gland and influence over certain aspects of human light-dark circadian rhythms.

As another example, cholecystokinin (CCK) is an intestinal hormone whose main function is, upon detection of fats entering the duodenum, to hormonally signal the gallbladder to contract and the stomach to slow down the speed of digestion so the small intestine can effectively digest the fats. However, recently CCK has been found to have dopamine-enhancing effects in the brain (which has its own CCK receptors!) which affect mental status, movement coordination, and appetite.

These are only a few examples from hundreds in the scientific literature. The brain, specifically the hypothalamus, plays a highly critical role in the regulation of energy metabolism, nutrient metabolism, and the control of feeding behaviors. The gastrointestinal tract is intimately connected to the actions of the hypothalamic-pituitary axis via the release of a plethora of peptides that exert responses within the brain.

Conclusion

This paper simply poses the question why there could not be a similar factor produced in the duodenal mucosa which might regulate the production of thyroxine (T4) through the agency of the hypothalamus, anterior pituitary, or other brain region? The rationale to conduct research in this direction is the emphasis placed by the Ayurvedic sages on the connection between jatharāgni (in the gut) and dhatvagni (disseminated throughout every tissue) and, in particular, the contribution the former is known to make to the latter. The views of the ancient sages on this subject are worthy of our unrestrained consideration, as they come from pure truth-seekers who have transcended all passion and ignorance by means of sadhana and knowledge. Their understanding of life is eternal, complete and untainted truth. They do not give expression to what is not truth. The verses recorded in the ancient texts are the guiding light for we who humbly follow in their footsteps.