Postgrad Med J: first published as 10.1136/pgmj.63.742.661 on 1 August 1987. Downloaded from Postgraduate Medical Journal (1987) 63, 661-663

Clinical Reports

Myopathy in acute hypothyroidism

A.W.C. Kung, J.T.C. Ma, Y.L. Yu, C.C.L. Wang, E.K.W. Woo, K.S.L. Lam, C.Y. Huang and R.T.T. Yeung Department ofMedicine, University ofHong Kong, Queen Mary Hospital, Pokfulam Road, Hong Kong.

Summary: Hypothyroid myopathy has so far been reported in long standing cases ofhypothyroidism. We describe two adult patients with myopathy associated with acute transient hypothyroidism. Both presented with severe muscle aches and cramps, stiffness and spasms. Muscle enzymes were markedly elevated and electromyography in one patient showed myopathic features. Histological changes were absent in muscle biopsy, probably because of the short duration of metabolic disturbance. The myopathy subsided promptly when the hypothyroid state was reversed.

Introduction Hypothyroid myopathy has been described in patients however no muscle weakness or symptoms of hypo- with long-standing hypothyroidism.' 3 We report two thyroidism. She had no preceding viral infection.

Chinese patients with muscle involvement in acute Examination revealed that the goitre had decreased in copyright. transient hypothyroidism, who improved after rever- size and she was clinically euthyroid. Motor and sal of the hypothyroid state, sensory functions were completely normal. Investigation showed a T4 of 44nmol/l, triiodo- thyronine (T3) 1.2 nmol/I (normal 0.77-2.97 nmol/1), Case reports and TSH 5.1 AIU/ml (normal up to 7). The serum creatine kinase level was 11,940ILmol/min.l (normal Case I 5-165) and the lactic dehydrogenase was 397;Lmol/ min.l (normal 130-275), and glutamic-oxalacetic A 42 year old woman presented at another hospital transaminase was 120limol/min.l (normal 28-32). with a one-month history of heat intolerance, hand Serum sodium and potassium were normal. The http://pmj.bmj.com/ tremors, weight loss, palpitations and sweating. The trichinella and cysticercosis antibody titres and serial thyroid gland was diffusely enlarged to two times in viral antibody titres for viruses likely to cause myositis size. Her serum thyroxine (T4) level was raised at were negative, as were anti-nuclear antibody, 237 nmol/l (normal:58-154). Graves' disease was rheumatoid factor, anti-smooth muscle and anti- diagnosed and she was treated with carbimazole 30 mg striated muscle antibodies. The ischaemic lactate test daily together with propranolol 60mg daily for 4 showed no abnormality. Electromyography (EMG)

weeks. She was seen again 6 weeks later and was noted was performed on the right deltoid, biceps, vastus on October 6, 2021 by guest. Protected to be clinically euthyroid. The serum T4 was 47 nmol/l medialis and iliopsoas. Myopathic changes were and the thyroid stimulating hormone (TSH) raised at found only in the iliopsoas muscle: a full interference 12 p1U/ml (normal up to 7). The dosage ofcarbimazole pattern with small spiky polyphasic units less than was lowered to 20 mg daily and propranolol stopped. 500 fLV. A needle biopsy performed over the left Eight weeks after starting treatment she was deltoid muscle was normal under both light and referred to our unit because of painful cramps and electron microscopy. spasms involving muscles of the shoulder and pelvic With a low T4 level and the exclusion ofother causes girdles. The attacks came on spontaneously or with of painful myopathy, the diagnosis of hypothyroid mild exertion, with severe pain lasting for 10 minutes myopathy was made. Carbimazole was discontinued and gradually wearing off over 2 hours. There was and within one week, her symptoms subsided, the muscle enzymes returned to normal and thyroid Correspondence: A.W.C. Kung function also became normal (T4 of 98 nmol/1 and Accepted: 3 February 1987 TSH of 1.2 jIdU/ml). Her thyrotoxic symptoms Q The Fellowship of Postgraduate Medicine, 1987 Postgrad Med J: first published as 10.1136/pgmj.63.742.661 on 1 August 1987. Downloaded from 662 CLINICAL REPORTS recurred 2 weeks later and carbimazole at 30 mg/day stiffness and difficulty in relaxation of muscles with with thyroxine 50 pg/day and propranolol 30 mg/day typical myotonic response to contraction, percussion, daily was restarted. With this regime, there was no and electrical stimulation after thyroidectomy. In recurrence of the painful myopathy over a follow-up Hoffman's syndrome, the patients typically complain period of 4 months. of cramps, ache and pain in muscles of the shoulder and pelvic girdles. They have enlarged muscles, weak- Case 2 ness, slow movements and delayed relaxation of tendon reflexes. Although the Kocher-Debre- A 38 year old man presented with a weight loss of 13 kg Semelaigne syndrome and Hoffman's syndrome were and heat intolerance for 3 months. The thyroid gland initially described in different age groups, some auth- was one and a half times enlarged. A diagnosis of ors regard them as variants of the same disease Graves' disease was made. Serum T4 was 287 nmol/I process.',7,8 and free thyroxine index (FTI) 284 (normal 76-152). Elevation of the serum creatine kinase in hypothy- Radioactive iodine 315 MBq was given and he became roidism is common, and the level is proportional to euthyroid 4 months afterwards. However, T4 repeated the degree of the hypothyroid state.9 Electromyogra- one year later was 208 nmol/I with FTI 236 and so a phic abnormalities are also common with an overall second dose of 150 MBq radioactive iodine was given. incidence of 61%.'° These usually take the form of When seen again 6 weeks later, he complained of myopathic changes with frequent small-amplitude and tiredness and muscle cramps. T4 was only 27 nmol/I short-duration polyphasic motor units on moderate with TSH of 1.2 fdU/ml. He was admitted 3 days later volition. A myotonic-like reaction or pseudomyotonia for severe generalized muscle stiffness and weakness. has rarely been described, being differentiated from He was unable to move any ofhis limbs and the muscle true myotonia by the absence of the classical waxing would go into spasm whenever that part was being and waning characters seen in the latter.7"' The moved. The spasm was so severe that on one occasion mounding phenomenon ofmyxoedema on percussion he could not brake his car resulting in a collision. of the exposed muscles is electrically silent on EMG.'2 There was clumsiness of movement and weakness of Histologically, muscle fibre enlargement, focal

girdle muscles together with myotonic-like reaction. myofibrillar degeneration, increases in central nuclei,copyright. The muscle bulk was increased and all muscles felt stiff glycogen and mitochondrial aggregates, subsarcolem- and firm. There was delay in relaxation of the bicep mal accumulations of lipofuscin are present.'3"14 There and ankle reflexes. is also dilatation of the sarcoplasmic reticulum and Laboratory investigation revealed elevated muscle proliferation ofthe T-system. Some authors described enzymes (creatine kinase 7290 jimol/min. 1). Serum T4 an increase in Type I fibre area and selective atrophy of was undetectable on two occasions and TSH was Type II fibres, together with low mitochondrial 361IU/ml. EMG of the right deltoid, biceps, vastus enzyme activities. The mitochondrial abnormalities medialis and iliopsoas did not reveal myotonia or are postulated to be due to metabolic disturbances in myopathic changes. The patient refused a muscle oxidative phosphorylation.'5"6 Upon treatment with biopsy. The clinical picture was compatible with thyroxine, the symptomatology, creatine phosphokin-http://pmj.bmj.com/ Hoffman's syndrome. Thyroxine was started at 50 pg/ ase, the EMG changes and the muscle morphology all day together with triiodothyronine 60 pg/day. His revert back to normal.'6"7"8 muscle power showed marked improvement and his Myopathy may occur in patients with hypoth- muscle cramps and stiffness gradually subsided over yroidism of idiopathic,'9 or familial cases,20 post- one month. The muscle bulk also reverted to normal. thyroid irradiation,2' post-Hashimoto's thyroiditis,22 Triiodothyronine was stopped 3 months later and the post-thyroidectomy,3 and post-radioactive iodine thyroxine dosage was gradually increased to 150 All the cases so far pg/ therapy hypothyroidism.23 reported on October 6, 2021 by guest. Protected day. His thyroid function returned to normal 4 months had long duration of hypothyroidism with florid after the onset of muscle stiffness. features of myxoedema and a very low T4 level. Our two patients had only a short period of biochemical hypothyroidism - 2 weeks in the first and 6 weeks in Discussion the second. Moreover, the degree of hypothyroidism was very mild in the first patient. Thus, while there was Myopathy is a known complication of long-standing marked elevation of muscle enzymes, EMG only hypothyroidism and the incidence of musculoskeletal showed mild myopathic changes, and the muscle symptoms varies from 30-80% in different series.456 biopsy was normal. The explanation may be that Kocher' and Debre & Semelaigne2 described a syn- morphological changes in the muscles have not taken drome of muscular hypertrophy associated with place within the short duration of mild hypoth- delayed muscle relaxation in two athyreotic cretins. yroidism. In a study with rabbit, histological changes Hoffman3 in 1897 reported an adult who developed cannot be detected till 4 to 8 weeks after thyroidec- Postgrad Med J: first published as 10.1136/pgmj.63.742.661 on 1 August 1987. Downloaded from CLINICAL REPORTS 663 tomy.24 In the second case, although the duration of tomy, or a few months after radioactive iodine therapy hypothyroidism was also relatively short, the degree of for Graves' disease. The majority of these patients hypothyroidism was profound and hence the full tend to be clinically euthyroid, and their thyroid picture ofHoffman's syndrome was produced. In both function usually normalises once the thyroid gland has patients, the muscle enzymes were markedly elevated recovered from the insult or when the anti-thyroid when the T4 levels were low, but returned to normal drug is withdrawn. We suggest that myopathy in acute upon being rendered euthyroid. transient hypothyroidism is not rare and should be Acute transient hypothyroidism is encountered considered as a differential diagnosis of painful frequently in acute thyroiditis due to lymphocytic myopathy in the appropriate clinical setting. Our thryoiditis or de Quervain's thyroiditis and over-treat- patients, particularly the first one, illustrate that the ment in Graves' disease and Hashimoto thyrotox- dramatic symptoms of myopathy may be the initial icosis. It may also occur immediately after thyroidec- presentation in acute hypothyroidism.

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