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PubMed1979

Red cell changes in hyperthyroidism.

The Coulter 'S' red cell profile was studied prospectively in 100 untreated non-anaemic hyperthyroid patients and followed up in 52 of them until they had become euthyroid with radio-iodine or carbimazole treatment. Serial haematological data were also obtained in 23 hyperthyroid patients during treatment with beta-adrenoreceptor blocking drug alone. The most significant finding was a low mean corpuscular volume (MCV) which was invariably present throughout the hyperthyroid state. Treatment with beta-adrenoreceptor blocking drugs did not significantly alter any of the red cell parameters. On the other hand, the MCV increased and was restored to normal with radio-iodine or carbimazole treatment although there was a lag period of about 6--8 weeks between achieving the euthyroid state and the normalisation of this red cell index. While none of the patients were aneaemic, the haemoglobin level rose significantly following effective anti-thyroid treatment. It is suggested that measurement of the MCV may have a useful role in the diagnosis of hyperthyroidism. 2 possible mechanisms leading to the observed red cell changes in hyperthyroidism are postulated.

Adolescent↗

PubMed2000

Feline hyperthyroidism: spectrum of clinical presentions and response to carbimazole therapy.

OBJECTIVE: To determine the spectrum of clinical presentations of hyperthyroidism in cats and response to carbimazole therapy by analysis of historical, clinical and laboratory data. DESIGN: A prospective clinical study involving client-owned cats presenting to a private veterinary practice in Australia. PROCEDURE: Twenty-five cats diagnosed as hyperthyroid during a 23-month period participated in the study with owner consent. Therapy with carbimazole was instituted and revisits were scheduled 2, 6 and 13 weeks after diagnosis. The cats were physically examined and underwent haematological and serum biochemical testing at each revisit. Owners were also asked to assess clinical signs in their cats in the periods between veterinary examinations. Cats with underlying renal disease were managed by alterations or cessation of carbimazole therapy. RESULTS: A high prevalence of lethargic or inappetent cats without detectable underlying nonthyroidal illness was found. There was also a high prevalence of cats less than 10-years-old and cats in good body condition. Fourteen cats treated with carbimazole and monitored for 13 weeks responded favourably to therapy. Side-effects were minor and uncommon. Cats with underlying renal disease that became apparent during the study, responded well to alterations or cessation of carbimazole therapy. CONCLUSION: The trend towards more subtle clinical presentations of hyperthyroid cats reported previously continued in this study. The findings of the current study do not appear to support the traditional view of hyperthyroid cats as being old, hyperactive, hungry and thin. Carbimazole therapy was found to decrease the prevalence of almost all clinical abnormalities in 14 cats and side-effects were minor and uncommon. This study demonstrates the usefulness of medical management of hyperthyroidism in the cat when radioiodine therapy is not possible due to renal compromise or other factors.

Animals↗

PubMedDate not supplied

Triiodothyronine (T3) suppression test. An aid in the diagnosis of mild hyperthyroidism in cats.

The purpose of this study was to develop a T3 suppression test to help in the diagnosis of mild hyperthyroidism in cats. We evaluated the response in circulating T4 concentrations to exogenous T3 (liothyronine) administration in 44 clinically normal cats, 77 cats with hyperthyroidism, and 22 cats with nonthyroidal disease. The test was performed by first collecting blood samples for basal serum T4 and T3 determinations, administering liothyronine at an oral dosage of 25 micrograms three times daily for seven doses, and, on the morning of the third day, again collecting serum samples for T4 and T3 determinations 2 to 4 hours after the seventh dose of liothyronine. The mean basal serum concentrations of T4 (53.1 nmol/L) and T3 (1.8 nmol/L) were significantly higher in the cats with hyperthyroidism than in the normal cats (T4 = 25.3 nmol/L, T3 = 1.3 nmol/L) and the cats with nonthyroidal disease (T4 = 29.5 nmol/L, T3 = 1.4 nmol/L); however, there was a great deal of overlap of basal values between the three groups of cats. Of the 77 cats with mild hyperthyroidism, 41 (53%) had serum T4 values and 55 (71%) had T3 values that were within the established normal ranges. After administration of liothyronine, mean serum T4 concentrations fell much more markedly in the normal cats and the cats with nonthyroidal disease than in the hyperthyroid cats.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1983

The effect of hyperthyroidism on capillarity and oxidative capacity in rat soleus and gastrocnemius muscles.

Muscle fibre composition and capillarity were evaluated in frozen sections stained for myosin ATPase of the soleus and the white area of the medial head of the gastrocnemius of rats made hyperthyroid by injections of triiodothyronine (300-400 micrograms/kg body weight, every other day) for 2, 3 and 4 weeks. O2 consumption of homogenates of these muscles in the presence of excess inorganic phosphate (Pi) and ADP with pyruvate and malate as substrates was also measured. Increased oxidative capacity was observed in the soleus homogenates of hyperthyroid animals after 2 weeks of treatment while no changes were observed in the oxidative capacity of the homogenates of the white area of the medial head of the gastrocnemius, even after 4 weeks of treatment. Hyperthyroid animals showed a greater capillarity than controls in both muscles. In the soleus this was evident after 2 weeks of treatment while in the white area of the medial head of the gastrocnemius, it was evident only after 4 weeks of treatment. Fibre composition was affected in the soleus after 4 weeks of treatment. In control animals two fibre types were present in the soleus: slow-twitch oxidative fibres (s.o. or type I fibres) with a high ATPase activity after acid pre-incubation and fast-twitch glycolytic oxidative fibres (f.o.g. or type IIa fibres) with a low ATPase activity after acid pre-incubation. In the soleus of the hyperthyroid animals, a third fibre type with intermediate ATPase activity after acid pre-incubation was also present. This most probably represents a change in the type of myosin being synthesized by some fibres. No changes in fibre composition were observed in the white area of medial head of the gastrocnemius which was made up of only fast-twitch glycolytic fibres (f.g. or type IIb fibres). The changes in oxidative capacity and capillarity in the soleus preceded and did not seem to be related to the changes in the type of myosin being synthesized. The increased capillarity found in the white area of the medial head of the gastrocnemius of the hyperthyroid animals, in the absence of an increase in the oxidative capacity, indicates that the latter is not the only factor that determines capillarity in skeletal muscle.

Adenosine Triphosphatases↗

PubMed1984

Hyperthyroidism due to inappropriate TSH secretion with associated hyperprolactinaemia--a case report and review of the literature.

A patient with inappropriate thyrotrophin (TSH) secretion is described. She initially presented with classical hyperthyroidism during pregnancy, responded to propylthiouracil and, subsequently, had a normal delivery. Hyperthyroidism persisted and 7.5 months later a subtotal thyroidectomy was performed. After a further 16 months, mild symptoms of hyperthyroidism recurred. She again responded to propylthiouracil, but developed galactorrhoea. At that stage, it was noted that she had persistently elevated circulating TSH in the presence of elevated T4 and T3 levels. Her symptomatology was mild, although objective indices of thyroid activity, including pulse rate, BMR, sex hormone binding globulin and cholesterol, were indicative of hyperthyroidism. CT scan and tomography of the sella were normal. She had a markedly exaggerated TSH response to thyrotrophin releasing hormone (TRH). Basal TSH and responsiveness to TRH was suppressed by high dose dexamethasone. The TSH response to TRH was partially suppressed by exogenous T3, but there was no effect on basal TSH levels. TSH also decreased slightly with L-dopa and bromocriptine. Circulating TSH rose markedly during methimazole administration. TSH alpha and beta subunits were elevated and appropriate for the high TSH. In addition, both subunits increased following TRH. The patient had basal hyperprolactinaemia with an impaired prolactin (PRL) response to TRH and metoclopramide. PRL suppressed with L-dopa and bromocriptine. The remaining anterior pituitary function was intact. Most of the laboratory findings argue against the presence of a TSH producing pituitary tumour and the most likely cause for inappropriate TSH secretion in this patient is selective resistance of the thyrotroph to thyroid hormones. A mild element of peripheral resistance might also be present. The hyperprolactinaemia could be related to lactotroph resistance to thyroid hormone. The complexities of treatment in this patient are stressed. Therapy was initially attempted with low dose dexamethasone, but this had no effect. T3 treatment produced an exacerbation of her symptomatology and did not influence basal TSH, thyroid hormones, or 131I uptake. Bromocriptine administration for 11 months partially suppressed basal TSH without influencing T3 and there was an increase in T4. Methimazole did decrease her T4 and T3, but TSH and PRL rose to even greater levels. Her hyperthyroidism was eventually controlled with an ablative dose of 131I. Thyroid hormone will be given in an attempt to suppress her TSH.

Adult↗

PubMed1977

Metabolism of monoamines and diamines in hyperthyroid and hypothyroid rats.

The in vivo rates of catabolism of 14C-labelled pentylamine, ethylamine, putrescine, and cadaverine were studied in thyroidectomized rats and others made hyperthyroid by the daily administration of 0.2 mg of L-thyroxine per kilogram for 20--21 days. Hyperthyroid rats metabolized the monoamines at an accelerated rate; thyroidectomized animals oxidized pentylamine at a reduced rate. There was no effect of hypophysectomy on the rate of pentylamine oxidation. The in vitro monoamine oxidase (MAO) activity of liver was reduced in hyperthyroid rats and unchanged in those thyroidectomized; MAO activity in skeletal muscle was increased in the hyperthyroid rats and decreased in the hypothyroid rats. Because of the large mass of skeletal muscle compared with liver, it is considered that the changes in muscle MAO could play an important role in determining the rate of oxidation of pentylamine in vivo. The oxidation of the two diamines tested was not significantly affected by thyroidectomy; the rates were increased in the hyperthyroid rats, but the increase was significant only for cadaverine.

Amines↗

PubMed1995

Involvement of renin-angiotensin system in the reduced pressure natriuresis response of hyperthyroid rats.

Previous studies have indicated that the pressure diuresis and natriuresis (PDN) response is greatly impaired in thyroxine-treated hypertensive rats. In the present study, we have examined the role of the renin angiotensin system (RAS) as a mediator of these alterations by characterizing the relationships between renal perfusion pressure and urine flow and sodium excretion in hyperthyroid rats acutely treated with a converting-enzyme inhibitor (captopril, 2 mg/kg) or an AT1 angiotensin II receptor blocker (losartan, 10 mg/kg). In the control animals, captopril did not change mean arterial pressure (MAP) or renal blood flow (RBF) but significantly decreased MAP and increased RBF and glomerular filtration rate in the hyperthyroid rats. Captopril did not change the PDN response of the control animals but improved significantly that of the hyperthyroid rats, although it was not completely normalized. Losartan also significantly improved renal hemodynamics and excretion in hyperthyroid rats. These results indicate that an increased intrarenal activity of the RAS is partly responsible for the blunted renal PDN mechanism of the hyperthyroid rats.

Animals↗

PubMed1995

Response of leucine metabolism to hyperinsulinemia under amino acid replacement in experimental hyperthyroidism.

We investigated the responsiveness of protein metabolism to insulin as a mediator of the protein catabolic response to hyperthyroidism in humans. Six healthy volunteers were studied in a postabsorptive state before and after oral intake of thyroid hormones (2 micrograms.kg-1.day-1 L-thyroxine for 6 wk along with 1 microgram.kg-1.day-1 triiodothyronine for the last 2 wk). Insulin was infused at 7.14 nmol.kg-1.min-1 for 140 min under euglycemic and eukalemic clamps. An appropriate amino acid infusion was used to blunt insulin-induced hypoaminoacidemia. Leucine kinetics were assessed using a primed continuous infusion of L-[1-13C]leucine. Hyperthyroidism induced a significant increase (P < 0.05) in leucine endogenous appearance rate (a reflection of proteolysis; 2.15 +/- 0.06 vs. 1.76 +/- 0.03 mumol.kg-1.min-1 in the control state), oxidation (0.54 +/- 0.04 vs. 0.47 +/- 0.07), and nonoxidative disposal (a reflection of protein synthesis; 1.80 +/- 0.06 vs. 1.45 +/- 0.06). Insulin lowered proteolysis. Further hyperthyroidism improved the ability of insulin to inhibit proteolysis, whether considered as an absolute decrease (-0.57 +/- 0.02 vs. -0.45 +/- 0.05 mumol.kg-1.min-1, P < 0.05) or related to insulinemia [1.59 +/- 0.11 vs. 1.01 +/- 0.08 mumol leucine.kg-1.min-1/(nmol insulin/l), P < 0.05]. Insulin also moderately (but significantly P < 0.05) lowered protein synthesis in both control and hyperthyroid states. These changes in insulin action may provide a mechanism to save body protein during hyperthyroidism.

Adult↗

PubMed1987

Increased myocardial beta-receptors and adrenergic responses in hyperthyroid pigs.

Controversy exists presently as to whether thyroid hormone potentiates the action of catecholamines on the heart. Therefore, the relationships between adrenergic sensitivity, myocardial beta-receptor number, and the cardiovascular responses associated with excess thyroid hormone were investigated in pigs (Sus scrofa). A hyperthyroid state was induced by the administration of triiodothyronine (T3; 1 mg/kg iv). After 7 days there was a significant increase in resting heart rate, systolic blood pressure, rate-pressure product, and O2 consumption in the hyperthyroid state. At this time echocardiography showed a substantial increase in myocardial cross-sectional size. Pharmacological tests showed an increased intrinsic heart rate (127 +/- 29 to 205 +/- 25 beats/min; P less than 0.001) and an increased chronotropic sensitivity to isoproterenol. The concentration of isoproterenol required for a 50% of maximal response (ED50) was reduced by 33 +/- 30% (2.1 +/- 1.0 to 1.2 +/- 0.3 micrograms/l; P less than 0.025). The slope of the line relating isoproterenol concentration and change in heart rate was increased by 29 +/- 33% (61 +/- 10 to 78 +/- 10; P less than 0.025). Radioligand studies demonstrated an increase in the number of beta-receptors in right atrial membranes from hyperthyroid animals (41 +/- 7 vs. 75 +/- 18 fmol/mg; P less than 0.02). The apparent dissociation constant (KD) of the receptor for l-isoproterenol was similar in membranes from euthyroid and hyperthyroid animals (157 +/- 57 vs. 219 +/- 59 nM, respectively; P = NS). This study demonstrates that hyperthyroidism is associated with an increased chronotropic sensitivity to isoproterenol, consequent to an up-regulation of beta-adrenergic receptors in the right atrium.

Animals↗

PubMed1991

Competitive control of myosin expression: hypertrophy vs. hyperthyroidism.

The competition between two opposing influences on the phenotypic expression of skeletal muscle myosin were studied to determine which was the dominant regulator. Experimental hyperthyroidism, which induces fast myosin expression, was produced by subcutaneous implantation of a 40-day constant-time-release triiodothyronine pellet. Compensatory hypertrophy, which induces slow myosin expression, was produced by surgical removal of a synergistic hindlimb muscle. Hyperthyroidism increased the percentage of type II fibers and the fast myosin isoforms in both the plantaris and soleus muscles. Hypertrophy significantly increased the percentage of type I fibers and the slow myosin type in the plantaris and soleus muscles. However, with the simultaneous introduction of hyperthyroidism and hypertrophy, only the hyperthyroid effects were observed. Hyperthyroidism and not physiological demand was found to be the dominant regulator of skeletal muscle myosin expression.

Adaptation, Physiological↗

PubMed2003

Thyroid cancer in patients with hyperthyroidism.

OBJECTIVE: The coexistence of hyperthyroidism and thyroid cancer is considered a rare event. With the aim of assessing the clinical relevance of this association, we have retrospectively analyzed the incidence of thyroid cancer in 425 hyperthyroid patients seen and treated by surgery in our institutions. METHODS: Among these hyperthyroid patients, we observed 241 (56.7%) cases of multinodular toxic goiter, 120 (28.3%) of uninodular toxic goiter and 64 (15%) cases of Graves' disease. RESULTS: Thyroid cancer was diagnosed in 7 (1.65%) hyperthyroid patients. Histological examination revealed the presence of papillary carcinoma in 5 cases and follicular carcinoma in 2 cases. Neoplasia was detected in 4 patients with nodular toxic goiter and in 3 with uninodular toxic goiter. None of the patients with Graves' disease had thyroid cancer. During the follow-up of 74 months (range 4-154), there were no deaths or any recurrences. CONCLUSION: Although the occurrence of thyroid cancer in hyperthyroid patients is a rare event, the presence of a 'cold' nodule in a hyperfunctioning thyroid should be carefully evaluated to exclude the presence of concurrent malignancy.

Adenocarcinoma, Follicular↗

PubMed2005

Long-term carbimazole treatment of neonatal nonautoimmune hyperthyroidism due to a new activating TSH receptor gene mutation (Ala428Val).

BACKGROUND: Hereditary nonautoimmune hyperthyroidism is caused by activating germline mutations in the thyrotropin receptor gene. Antithyroid treatment failed to control hyperthyroidism in most cases, so that primary thyroid ablation or 131I therapy is advocated as the preferred treatment of choice. PATIENT/METHODS: We describe a case of neonatal nonautoimmune hyperthyroidism treated with carbimazole. Molecular analysis revealed a new heterozygous point mutation (A428V) in the TSH receptor (TSHR) gene. RESULT: Antithyroid treatment was successful in controlling hyperthyroidism for the first 5.9 years of age. CONCLUSION: We conclude that carbimazole therapy is effective in treating nonautoimmune hyperthyroidism. It may be an alternative to thyroidectomy or radioiodine treatment.

Antithyroid Agents↗

PubMed1992

Bone turnover in overt and subclinical hyperthyroidism due to autonomous thyroid adenoma.

Parameters of bone turnover were measured in 20 premenopausal women affected by autonomous thyroid adenoma: 7 patients were suffering from overt hyperthyroidism with raised values of free thyroid hormones; 13 were clinically euthyroid and had normal values of free thyroid hormones. In all cases serum TSH concentrations were below the lower normal limit of our laboratory (< 0.4 mU/l). Eleven healthy premenopausal women were studied as a control group. Patients with overt hyperthyroidism disclosed a significant enhancement of both bone resorption (increased serum calcium and urinary excretion of hydroxyproline) and bone formation (increased serum levels of osteocalcin and alkaline phosphatase) when compared both to controls and to patients with subclinical hyperthyroidism. No significant alterations of bone metabolism parameters were found in patients with subclinical hyperthyroidism in comparison with controls. Therefore, in premenopausal women affected by autonomous thyroid adenoma the bone turnover appeared to be significantly increased when the serum values of free thyroid hormones were raised in the group of patients with overt hyperthyroidism.

Adenoma↗

PubMed1990

The hyperthyroid heart. An analysis of systolic and diastolic properties in single rat ventricular myocytes.

Single ventricular myocytes were isolated by collagenase digestion from the hearts of 6-8-month-old male Wistar rats in either the control (euthyroid) state or after 7 days of daily injection of 0.64 mg/kg thyroxine (hyperthyroid). Myocytes were field-stimulated from slack length, and contraction was measured with an inverted microscope-photodiode array-computer apparatus. The effect of pacing rate and ouabain administration on systolic and diastolic function was examined. Single myocytes isolated from hyperthyroid hearts maintain the properties of bulk muscle, because maximal twitch velocity is augmented 98% and the time course of contraction as measured by the time to peak shortening, relaxation time, or contraction duration is abbreviated 39%. Spontaneous sarcoplasmic reticulum calcium release, as measured by the occurrence of contractile waves, is increased in the hyperthyroid myocytes. This increased frequency of spontaneous sarcoplasmic reticulum calcium release is most marked under conditions known to be associated with high intracellular calcium, such as low pacing rates or digitalis glycoside administration. It can account for the hypoperformance of the hyperthyroid myocytes noted under these conditions because it is associated with depletion of sarcoplasmic reticulum calcium stores and diminution of subsequent twitch amplitude. These observations may help explain, in part, the cellular basis of the altered cardiac performance in the hyperthyroid state.

Animals↗

PubMed2004

Changes of noradrenergic activity and lipolysis in the subcutaneous abdominal adipose tissue of hypo- and hyperthyroid patients: an in vivo microdialysis study.

Thyroid function plays an important role in the regulation of overall metabolic rate and lipid metabolism. However, it is uncertain whether thyroid hormones directly affect lipolysis in adipose tissue and to what extent those changes contribute to overall metabolic phenotype. Our study was designed, using the microdialysis technique, to determine basal and isoprenaline-stimulated local lipolysis and to determine local concentrations of lipolysis-regulating catecholamines in abdominal subcutaneous adipose tissue in 12 patients with hypothyroidism, 6 patients with hyperthyroidism, and 12 healthy control subjects. Plasma norepinephrine (NE) concentrations in hypothyroid subjects were significantly higher than in the control and hyperthyroid groups. In contrast, systemic, adipose NE levels in hypothyroid patients were decreased relative to controls. Hyperthyroidism, on the other hand, resulted in four-fold higher adipose NE levels. Basal lipolysis measured by glycerol concentrations in adipose tissue was significantly attenuated in hypothyroid patients and markedly increased in hyperthyroid patients in comparison with the control group. In addition to differences in basal lipolysis, hypothyroidism resulted in attenuated, and hyperthyroidism in enhanced, lipolytic response to local stimulation with beta(1,2)-adrenergic agonist isoprenaline. These results demonstrate that lipolysis in abdominal subcutaneous adipose tissue is strongly modulated by thyroid function. We suggest that thyroid hormones regulate lipolysis primarily by affecting local NE concentration and/or adrenergic postreceptor signaling.

Abdomen↗

PubMed2002

Elevated regional lipolysis in hyperthyroidism.

Hyperthyroidism is characterized by increased levels of circulating free fatty acids (FFA) and increased lipid oxidation, but it is uncertain which regional fat depots contribute. The present study was designed to define the participation of femoral and abdominal fat stores in the overall stimulation of lipolysis in hyperthyroidism in the basal state and during insulin stimulation. We studied nine women with newly diagnosed hyperthyroidism (HT) and after (euthyroidism, ET) medical treatment with methimazol and compared with eight control subjects (CTR). All subjects were studied in the postabsorptive state and during a 3-h hyperinsulinemic euglycemic clamp with microdialysis catheters sc in the abdominal and femoral adipose tissue. Before treatment, patients had elevated circulating concentrations of triiodthyronine, FFA, and glycerol. Levels of interstitial glycerol ( micro mol/liter) in abdominal adipose tissue [485 +/- 24 (HT), 226 +/- 20 (ET) (P < 0.001), 265 +/- 34 (CTR) (P < 0.001)] and in femoral adipose tissue [468 +/- 41(HT), 245 +/- 29 (ET) (P < 0.01), 278 +/- 31(CTR) (P < 0.005)] were elevated in the basal hyperthyroid state, and these differences prevailed during the glucose clamp [230 +/- 23 (HT), 113 +/- 13 (ET) (P < 0.01), 132 +/- 22(CTR) (P < 0.01) and 303 +/- 39 (HT), 122 +/- 15 (ET) (P < 0.01), 166 +/- 21(CTR) (P < 0.01)]. These results suggest that femoral and abdominal adipose tissue contribute equally to the excessive rate of lipolysis in hyperthyroidism and that both tissues are resistant to the actions of insulin.

Abdomen↗

PubMed2007

Approach to the patient with subclinical hyperthyroidism.

Endogenous subclinical hyperthyroidism, defined by normal circulating levels of free T4 and T3 and low levels of TSH, is a common clinical entity and is typically caused by the same conditions that account for the majority of cases of overt hyperthyroidism: Graves' disease, toxic multinodular goiter, and solitary autonomously functioning thyroid nodules. Subclinical hyperthyroidism has been associated with an increased risk of atrial fibrillation and mortality, decreased bone mineral density in postmenopausal women, and mild hyperthyroid symptoms. Treatment of subclinical hyperthyroidism remains controversial, given the lack of prospective randomized controlled trials showing clinical benefit with restoration of the euthyroid state. Nevertheless, it seems reasonable to treat older individuals whose serum TSH levels are less than 0.1 mU/liter and certain high-risk patients, even when the serum TSH is between 0.1 and the lower limit of the normal range.

Aged↗

PubMed1977

Transient recurrence of hyperthyroidism after delivery in Graves' disease.

Four patients with Graves' disease whose hyperthyroidism was in remission following antithyroid therapy were studied without any treatment during and after pregnancy. In the 8-9th month of pregnancy, they were in a euthyroid state with serum levels of thyroxine (T4) of 18.9, 11.9, 11.2 and 14.5 mug/100 ml, triiodothyronine (T3) of 273, 190, 162 and 244 ng/100 ml and T3 resin sponge uptake (RT3U) of 22, 14, 19 and 16% respectively (normal pregnant range: T4, 7.0-15.0, T3 140-250, RT3U 15-25). At 1-3 months after delivery, hyperthyroidism recurred, as manifested by T4 levels of 17.2, 14.5, 16.7 and 21.7 mug/100 ml, T3 levels of 320, 225, 390 and 464 ng/100 ml and RT3U levels of 34, 34, 43, and 41% respectively (normal non-pregnant range: T4 5.0-12.0, T3 90-190, RT3U 24-37). The recurrence of hyperthyroidism was also demonstrated by serial measurements of serum free T4 and free T3. The thyroid function of all four patients returned spontaneously to the normal range at 4-6 months after delivery. One patient developed hypothyroidism for a short period before regaining the euthyroid state. The titers of serum anti-thyroid microsomal antibodies and levels of serum immunoglobulins decreased during pregnancy and increased transitorily at the time of hyperthyroidism after delivery. Similarly, increases in the levels of thyroid hormones, anti-thyroid antibodies and immunoglobulins were observed transitorily following spontaneous abortion after 4 months' pregnancy in one case. We suggest that the transient recurrence of hyperthyroidism in Graves' disease may be induced by immunological changes after delivery.

Adult↗