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Fluoride = TSH

Fluoride = TSH
© 1996 – 2021 PFPC


During the late 1960s and throughout the 1970s many studies were conducted to investigate the effects of TSH on adenyl cyclase.

At this time it was commonly held that polypeptide hormones such as TSH produced many of their cellular effects by stimulating adenyl cyclase, thus increasing intracellular cAMP levels (Wolff & Jones, 1971; Wienand and Kohn, 1975). cAMP was, in turn, thought to exert its effects by activating protein kinases.

Fluoride had been found to be an activator of adenyl cyclase in many tissues, and investigators now used fluoride to learn more about TSH. These studies brought firm evidence that fluoride not only acted like TSH, but fluoride-stimulated cyclase activity could be many times higher than the optimal TSH stimulation, especially in carcinomas.

Like TSH, at low levels fluoride stimulated adenyl cyclase activity, while at higher doses it inhibited cyclase activation (Wolff & Jones, 1971; Wienand and Kohn, 1975; Jenq et al, 1993; Clark & Gerend, 1985).

As research continued, numerous investigations showed that – although fluoride was able to activate adenyl cyclase in homogenates in thyroid slices – it did not increase cyclic AMP levels as expected (i.e Zor et al, 1970), yet it produced the same effects as TSH. This finding led researchers to believe that TSH and fluoride effects, although identical, must have been obtained by different mechanisms (i.e Yamashita & Field, 1972). Research in the 1990s then brought evidence that TSH activated two G proteins at low levels – G(s) which stimulates adenyl cyclase, as well as Gq/11, which activate phospholipase C and are the calcium-transducing G proteins (Allgeier et al., 1994).

The discovery of G-proteins and the application of fluoride as the “universal G protein activator” brought much new knowledge to the field of signal transduction. The human TSH receptor was found to be the only known natural universal G-protein activator able to activate all four G protein families (Laugwitz et al, 1996). It was established that TSH-activation of adenyl cyclase was absolutely dependent on the regulatory G proteins (Totsuka et al, 1982, Utiger, 1996).

While many pro-fluoridation organizations and dental groups claim that the amounts of fluoride used in the TSH in-vitro experiments were 100 to 1000 times higher, and “such levels could never be obtained in humans”, they fail to realize that these experiments were made in isolated environments – specifically to investigate adenyl cyclase. TSH levels used in those experiments were also much higher than is ever found in humans. In the system, when other nucleotides are present, fluoride will  – just like TSH – activate adenyl cyclase at low concentrations, while inhibiting same at higher concentrations. This bi-phasic action is time-dependent and tissue-specific (see Jenq et al., 1993; Cohen-Luria et al., 1989).

Addendum 2020: Much higher doses are used in in vitro experiments because the levels of TSH receptors are much lower than they ever are in vivo. TSH receptor levels in the thyroid are 100-fold higher than in vitro (Boutin et al., 2020). The effects of TSH are dependent on TSH receptor expression and occupancy.

At slightly elevated TSH levels Gq/11 pathways are activated. Pathways downstream from Gq/11 activation are at the core of fluoride poisoning.

Selected studies using fluoride as TSH analogue

Abe Y – “Studies on the thyrotropin receptor and adenylate cyclase activity in various thyroid diseases: II. The properties of TSH receptor and adenylate cyclase in human thyroid tumors” Journal of the Endocrine Society of Japan 56(5):754-64 (1980)

Adler GM – “The effect of sialic acid on adenylate cyclase activity and thyrotropin-receptor binding in human thyroid membranes” Acta Biochim Pol. 25(4):343-7 (1978)

Ahn CS, Rosenberg IN – “Iodine metabolism in thyroid slices: effects of TSH, dibutyryl cyclic 3′,5′-AMP, NaF and prostaglandin E-1” Endocrinology 86(2):396-405 (1970)

Asbury RF, Cook GH, Wolff J – “Soluble adenylate cyclase from thyroid membranes” J Biol Chem 253(15):5286-92 (1978)

Bech K, Feldt-Rasmussen U, Madsen SN – “Influence of thyroglobulin on basal and stimulated human thyroid adenylate cyclase activity” J Clin Endocrinol Metab 53(2):264-9 (1981)

Bech K, Madsen SN – “Human thyroid adenylate cyclase in non-toxic goitre: sensitivity to TSH, fluoride and thyroid stimulating immunoglobulins” Clin Endocrinol (Oxf) 8(6):457-66 (1978)

Bidey SB,  Marshall MJ,  Ekins RP – Cyclic AMP release from normal human thyroid slices in response to thyrotrophin   Acta Endocrinol,  95: 335 – 340 (1980)

Birnbaumer L, Rodbell  A – “Adenyl Cyclase in Fat Cells. II. HORMONE RECEPTORS” J Biol Chem  244: 3477-3482 (1969)

Burke G – “Comparison of thyrotropin and sodium fluoride effects on thyroid adenyl cyclase” Endocrinology 86(2):346-52 (1970)

Burke G -“Effects of thyrotropin, sodium fluoride and ions on thyroid slice metabolism” Metabolism 19(1):35-42 (1970)

Carayon P, Guibout M, Lissitzky S – “Thyrotropin receptor-adenylate cyclase system in plasma membranes from normal and diseased human thyroid glands” J Endocrinol Invest 1(4):321-8 (1978)

Clark OH, Gerend PL – “Thyrotropin regulation of adenylate cyclase activity in human thyroid neoplasms” Surgery 97(5):539-46 (1985)

Clark OH, Gerend PL, Nissenson RA –  “Mechanisms for increased adenylate cyclase responsiveness to TSH in neoplastic human thyroid tissue” World J Surg 8(4):466-73 (1984)

Codaccioni JL, Carayon P, Michel-Bechet M, Foucault F, Lefort G, Pierron H – “Congenital hypothyroidism associated with thyrotropin unresponsiveness and thyroid cell membrane alterations” J Clin Endocrinol Metab 50(5):932-7 (1980)

Cohen-Luria R, Sigler L, Rimon G – “Biphasic effect of sodium  fluoride and guanyl nucleotides on binding to prostaglandin E2 receptors in rat epididymal adipocyte  membranes” Cell Signal 1(6):561-8 (1989)

Corvilain B, Laurent E, Lecomte M, Vansande J, Dumont JE – “Role of the cyclic adenosine 3′,5′-monophosphate and the phosphatidylinositol-Ca2+ cascades in mediating the effects of thyrotropin and iodide on hormone synthesis and secretion in human thyroid slices” J Clin Endocrinol Metab 79(1):152-9 (1994)
(First identification of pathways later ascribed to Gq/11)

DeEds F, Wilson RH, Cutting WC – “Thyrotropic hormone and fluorine activity” Endocrinology 26(6):1053-1056 (1940)

Delemer B, Dib K, Saunier B, Haye B, Jacquemin C, Correze C – “Alteration of the functional activity of Gs protein in thyrotropin-desensitized pig thyroid cells” Mol Cell Endocrinol 75(2):123-31 (1991)

Depauw H, De Wolf M, Van Dessel G, Lagrou A, Hilderson HJ, Dierick W – “Modification of the adenylate cyclase activity of bovine thyroid plasma membranes by manipulating the ganglioside composition with a nonspecific lipid transfer protein” Biochim Biophys Acta 1024(1):41-8 (1990)

Desmedt DH, Pochet R, Dumont JE- “Evidence for different modes of activation of thyroid adenylate cyclase” Arch Int Physiol Biochim 84(2):388-9 (1976)

Downs RW Jr, Levine MA, Drezner MK, Burch WM Jr, Spiegel AM – “Deficient adenylate cyclase regulatory protein in renal membranes from a patient with pseudohypoparathyroidism” J Clin Invest. 71(2):231-5 (1983)

Field JB, Bloom G, Kerins ME, Chayoth R, Zor U – “Activation of protein kinase in thyroid slices by thyroid-stimulating hormone” J Biol Chem 250(13):4903-10 (1975)

Fradkin JE, Cook GH, Kilhoffer MC, Wolff J – “Forskolin stimulation  of thyroid adenylate cyclase and cyclic 3′,5′-adenosine monophosphate  accumulation” Endocrinology 111(3):849-56 (1982)

Friedman Y, Wilger J, Crowell D, Burke G – “Effects of proteolytic enzymes and protease inhibitors on bovine thyroid adenylate cyclase activity” Endocrinology. 112(5):1674-9 (1983)

Gautvik KM, Gordeladze JO, Jahnsen T, Haug E, Hansson V, Lystad E – “Thyroliberin receptor binding and adenylyl cyclase activation in cultured prolactin-producing rat pituitary tumor cells (GH cells)” J Biol Chem 258(17):10304-11 (1983)

Giraud A, Siffroi S, Lanet J, Franc JL – “Binding and internalization of thyroglobulin: selectivity, pH dependence, and lack of tissue specificity” Endocrinology 138(6):2325-32 (1997)

Goldhammer A, Wolff J – “Interactions of fluoride and guanine nucleotides with thyroid adenylate cyclase” Biochim Biophys Acta 701(2):192-9 (1982)

Holmes SD, Titus G, Chou M, Field JB – “Effects of thyrotropin and cholera toxin on the thyroidal adenylate cyclase-adenosine 3′,5′-monophosphate system” Endocrinology 107(6):2076-81 (1980)

Inui T, Chen W, Okabe H, Ochi Y, Hachiya T, Nakajima Y, Kajita Y – “Production of thyroid stimulation blocking antibody without TSH receptor binding activity in rabbits with experimental autoimmune thyroiditis” Horm Metab Res. 26(1):5-8. doi: 10.1055/s-2007-1000763 (1994)

Jang D, Morgan SJ, Klubo-Gwiezdzinska J, Banga JP, Neumann S, Gershengorn MC – “Thyrotropin, but Not Thyroid-Stimulating Antibodies, Induces Biphasic Regulation of Gene Expression in Human Thyrocytes” Thyroid 30(2):270-276 (2020)

Jenq SF, Jap TS, Hsieh MS, Chiang H – “The characterization of adenyl cyclase activity in FRTL-5 cell line” Journal of the Chinese Medical Association 51(3):159-65 (1993)
“Sodium fluoride stimulation study demonstrated dual actions of fluoride on adenylate cyclase; when the cells were assayed with increasing concentration of NaF, the AC activity increased as the concentration of NaF increased from 0.01 to 1 mM, but decreased strikingly as that concentration increased from 1 mM to 100 mM.”

Juvenal GJ, Kleiman de Pisarev DL, Crenovich L, Pisarev MA. – “Role of neurotransmitters, prostaglandins and glucose on precursor incorporation into the RNA of thyroid slices” Acta Endocrinol (Copenh) 87(4):776-85 (1978)

Kalderon AE, Sheth V – “Secretion and adenylate cyclase in thyroid nodules” Arch Pathol Lab Med 102(7):381-86 (1978)

Kaneko T, Zor U, Field JB – “Thyroid-stimulating hormone and prostaglandin E1 stimulation of cyclic 3′,5′-adenosine monophosphate in thyroid slices” Science. 163(3871):1062-3 (1969)

Kendall-Taylor P – “Comparison of the effects of various agents on thyroidal adenyl cyclase activity with their effects on thyroid hormone release” J Endocrinol 54(1):137-45 (1972)

Lakey T, Mac Neil S, Humphries H, Walker SW, Munro DS, Tomlinson S – “Calcium and calmodulin in the regulation of human thyroid adenylate cyclase activity” Biochem J 225(3):581-9 (1985)

Laugwitz KL, Allgeier A, Offermanns S, Spicher K, Van Sande J, Dumont JE, Schultz G – “The human  thyrotropin receptor: a heptahelical receptor capable of stimulating  members of all four G protein families”  Proc Natl Acad Sci U S A 93(1):116-20 (1996)

Londos C, Salomon Y, Lin MC, Harwood JP, Schramm M, Wolff J, Rodbell M – “5′-Guanylylimidodiphosphate, a potent activator of adenylate cyclase systems in eukaryotic cells” Proc Natl Acad Sci U S A 71(8):3087-90 (1974)

Macchia V, Meldolesi MF, Chiariello M – “Adenyl-cyclase in a transplantable thyroid tumor: loss of ability to respond to TSH” Endocrinology 90(6):1483-91 (1972)

Macchia V, Mandato E, Carella C, Pisano G, Biscaglia G – “The adenylate cyclase-cyclic AMP-phosphodiesterase system in pathological human thyroid” J Endocrinol Invest 1(4):337-45 (1978)

Malkiewicz-Wasowicz B, Gamst O, Stromme JH – “The influence of changes in the phospholipid pattern of intact fibroblasts on the activities of four membrane-bound enzymes” Biochim Biophys Acta 482(2):358-69 (1977)

Mallet E, Carayon P, Amr S, Brunelle P, Ducastelle T, Basuyau JP, de Menibus CH – “Coupling defect of thyrotropin receptor and adenylate cyclase in a pseudohypoparathyroid patient” J Clin Endocrinol Metab
54(5):1028-32 (1982)

Marshall NJ, Von Borcke S, Malan PG – “Studies on inhibition of TSH stimulation of adenyl cyclase activity in thyroid plasma membrane preparations by propranolol” Endocrinology 96(6):1513-9 (1975)

Matsuzaki S, Pochet R, Schell-Frederick E – “A comparison of the subcellular distribution of 5′-nucleotidase, (Na+-K+)-ATPase and adenyl cyclase in beef thyroid gland” Biochim Biophys Acta 313(2):329-37 (1973)

Matsukura S, Kakita T, Fukase M, Fujita T – “Adenylate cyclase of a human medullary thyroid carcinoma”  Experientia 37(5):523-4 (1981)

Mizukami Y, Matsubara F, Matsukawa S – “Localization of adenylate cyclase and 5′-nucleotidase activities in human thyroid follicular cells” Histochemistry 74(1):9-19 (1982)

Moore WV, Wolff J – “Thyroid-stimulating hormone binding to beef thyroid membranes. Relation to adenylate cyclase activity” J Biol Chem 249(19):6255-63 (1974)

Nagai Y, Hosoya T – “Properties of the Na+, K+-stimulated adenosine triphosphatase system associated with the plasma membrane of pig thyroid glands”  J Biochem (Tokyo) 81(3):721-7 (1977)

Nitiyanant W, Dunlap D – “The subcellular localization of the long-acting thyroid stimulator inhibitor in bovine thyroid gland” Endocrinology 103(1):35-45 (1978)

Orgiazzi J, Chopra IJ, Solomon DH, Williams DE – “Comparison of the effect of TSH and fluoride on the adenylate cyclase activity of cold thyroid nodules” Ann Endocrinol (Paris) 37(2):107-8 (1976)

Pastan I, Macchia V, Katzen R – “Effect of fluoride on the metabolic activity of thyroid slices” Endocrinology 83(1):157-60 (1968)

Raspé E, Roger PP, Dumont JE – “Carbamylcholine, TRH, PGF2 alpha and fluoride enhance free intracellular Ca++ and Ca++ translocation in dog thyroid cells” Biochem Biophys Res Commun 141(2):569-77 (1986)

Rodesch F, Neve P, Willems C, Dumont JE – “Stimulation of thyroid metabolism by thyrotropin, cyclic 3′:5′-AMP, dibutyryl cyclic 3′:5′-AMP and prostaglandin E1” Eur J Biochem 8(1):26-32 (1969)

Sand G, Jortay A, Pochet R, Dumont JE – “Adenylate cyclase and protein phosphokinase activities in human thyroid. Comparison of normal glands, hyperfunctional nodules and carcinomas” Eur J Cancer 12(6):447-53 (1976)

Schorr I, Ney RL – “Abnormal hormone responses of an adrenocortical cancer adenyl cyclase” J Clin Invest 50(6):1295-300 (1971)

Shuman SJ, Zor U, Chayoth R, Field JB – ” Exposure of thyroid slices to thyroid-stimulating hormone induces refractoriness of the cyclic AMP system to subsequent hormone stimulation” J Clin Invest 57(5):1132-41 (1976)

Suzuki S, Widnell C, Field JB – “Preparation and characterization of subfractions of bovine thyroid plasma membranes”  J Biol Chem 252(9):3074-81 (1977)

Thode J, Børresen T, Beck K, Madsen SN – “Effect of furosemide on parathyroid hormone stimulated guinea pig renal adenylate cyclase and thyrotrophin and fluoride stimulated human thyroid adenylate cyclase” Acta Pharmacol Toxicol (Copenh) 49(4):285-9 (1981)

Thomas CG Jr, Combest W, McQuade R, Jordan H, Reddick R, Nayfeh SN – “Biological characteristics of adenomatous nodules, adenomas, and hyperfunctioning nodules as defined by adenylate cyclase activity and TSH receptors” World J Surg 8(4):445-51 (1984)

Toccafondi RS, Rotella CM, Tanini A, Fani P, Arcangeli P – “Thyrotrophin-responsive adenylate cyclase activity in thyroid toxic adenoma” Acta Endocrinol (Copenh) 92(4):658-68 (1979)

Tomura H, Itoh H, Sho K, Sato K, Nagao M, Ui M, Kondo Y, Okajima F – “Betagamma subunits of pertussis toxin-sensitive G proteins mediate A1 adenosine receptor agonist-induced activation of phospholipase C in collaboration with thyrotropin. A novel stimulatory mechanism through the cross-talk of two types of receptors” J Biol Chem 272(37):23130-7 (1997)

Totsuka Y, Nielsen TB, Field JB – “Effect of thyrotropin-induced desensitization of bovine thyroid adenylate cyclase on the nucleotide regulatory protein” Endocrinology 113(3):1088-95 (1983)

Totsuka Y, Nielsen TB, Field JB – “Roles of GTP and GDP in the  regulation of the thyroid adenylate cyclase system” Biochim Biophys  Acta 718 (2):135-43 (1982)

van Sande J, Cochaux P, Dumont JE – “Forskolin stimulates adenylate cyclase and iodine metabolism in thyroid” FEBS Lett 150(1):137-41 (1982)

Walinder O, Karlsson FA, Dahlberg PA – “Adenyl cyclase activity in human thyroid plasma membranes from normal human thyroid tissue and thyroid adenomas” Acta Endocrinol (Copenh) 92(1):95-104 (1979)

Willems C, Berberof-van Sande J, Dumont JE – “Inhibition of thyroid secretion by sodium fluoride in vitro” Biochim Biophys Acta 264(1):197-204 (1972)

Winand RJ, Kohn LD – “Stimulation of adenylate cyclase activity in retro-orbital tissue membranes by thyrotropin and an exophthalmogenic factor derived from thyrotropin” J Biol Chem 250: 6522 – 6526 (1975)

Wolff J,  Jones AB – “The Purification of Bovine Thyroid Plasma Membranes and the Properties of Membrane-bound Adenyl Cyclase” J Biol Chem 246:3939 -3947 (1971)

Wolff J, Cook GH – “Activation of thyroid membrane adenylate cyclase by purine nucleotides” J Biol Chem 10;248(1):350-5 (1973)

Wolff J, Cook GH – “Charge effects in the activation of adenylate cyclase” J Biol Chem 10;250(17):6897-903 (1975)

Yamashita K, Field JB – “Elevation of cyclic guanosine 3′,5′-monophosphate levels in dog thyroid slices caused by acetylcholine and sodium fluoride” J Biol Chem 247(21):7062-6 (1972)

Yamashita K, Field JB – “The role of phospholipids in TSH stimulation of adenylate cyclase in thyroid plasma membranes” Biochim Biophys Acta 304(3):686-92 (1973)

Zor U, Kaneko T, Lowe IP, Bloom G, Field JB – “Effect of thyroid-stimulating hormone and prostaglandins on thyroid adenyl cyclase activation and cyclic adenosine 3′,5′,-monophosphate” J Biol Chem 244(19):5189-95 (1969)

Further studies of interest:

Allgeier A, Offermanns S, Van Sande J, Spicher K, Schultz G, Dumont JE – “The human thyrotropin receptor activates G-proteins Gs and Gq/11” J Biol Chem 269(19):13733-13735 (1994)

Utiger AR – Editorial: “Thyrotropin-Receptor Mutations and Thyroid Dysfunction” NEJM 332(3):183-185 (1995)

Amr S, Menezez-Ferreira M, Shimohigashi Y, Chen HC, Nisula B, Weintraub BD – “Activities of deglycosylated thyrotropin at the thyroid membrane receptor-adenylate cyclase system” J Endocrinol Invest 8(6):537-41 (1985)

Boutin A, Neumann S, Gershengorn MC – “TSH Elicits Cell-Autonomous, Biphasic Responses: A Mechanism Inhibiting Hyperstimulation” Endocrinology 1;161(8):bqaa103 (2020)


Adenyl Cyclase – A membrane-bound enzyme that converts adenosine monophosphate to cyclic adenosine monophosphate (cAMP), an intracellular second messenger.

TSH – Short for thyroid-stimulating-hormone, also called thyrotropin, secreted by the anterior pituitary gland; activates adenyl cyclase (cAMP production) in thyroid cells leading to production and release of the thyroid hormones (T4 and T3). The TSH-receptor is the only G-protein-coupled receptor able to activate all G protein families, an activity directly mimicked by fluoride.

The graphs below were extracted from the study done by Wolff and Jones (1971), documenting the largely identical effects of fluoride and  TSH levels on the inhibition of adenyl cyclase in purified bovine thyroid plasma membranes (G(i) proteins):