Overt hyperthyroidism

Hyperthyroidism can be differentiated into overt and subclinical hyperthyroidism. Overt hyperthyroidism is diagnosed when the TSH level is suppressed, with free thyroxine (T4) and/or tri-iodothyronine (T3) levels above the normal reference range, in a person with symptoms of hyperthyroidism. Subclinical hyperthyroidism is diagnosed when the TSH level is suppressed, with free T4 and T3 levels within the normal reference range. The prevalence of overt hyperthyroidism is about 20 per 1000 women and 2 per 1000 men (including previously treated cases) with the annual incidence of overt hyperthyroidism is about 1 per 1000 women and is negligible for men. The prevalence of subclinical hyperthyroidism is 2% in adults, and 3% in those older than 80 years. 

Among 700 patients with multiple sclerosis treated with interferon beta-la (n = 467) or beta-lb (n = 233), overt hyperthyroidism occurred in five patients treated with interferon-beta-lb, three of whom required withdrawal and long-term carbimazole, while there were two cases of hypothyroidism and one of goiter without thyroid... 

Of 42 bipolar patients who had taken lithium for 4-156 months, three had subclinical hypothyroidism, three had subclinical hyperthyroidism, and one was overtly hyperthyroid (623). Ultrasonography showed that goiter was present in 38% and mild thyroid dysfunction was suggested in 48% because of an apparent increased conversion of free T4 to free T3. There was no correlation between the duration of lithium therapy and thyroid abnormalities. 

Of 42 bipolar patients who had taken lithium for 4—156 months, three had subclinical hypothyroidism, three had subclinical hyperthyroidism, and one was overtly hyperthyroid (256). Ultrasonography showed that goiter... 

Overtly hyperthyroid patients need to be pretreated with antithyroid drugs, as described above, before undergoing surgery in order to reduce perioperative mortality and morbidity. The exception is cases of thyroid storm, where emergency operation is scheduled within 48 h, because a delay would worsen the prognosis of the patient. 

The choice of treatment is discussed by the specialist and the patient. In the absence of one of the indications for surgery, we would suggest radioiodine treatment as the first choice. In case of overt hyperthyroidism, pretreatment with antithyroid drugs may be necessary. Optimum treatment modalities including the presence of a suppressed TSH in toxic adenoma or multinodular goiter should be established. On the one hand, patient s fears regarding radiation exposure and, on the other hand, possible surgical complication often infiuence the decision and have to be addressed. 

The therapeutic dosage of iodine is in the range of 100— 200 tg/day. Side-effects of low doses are rare and minor, consisting mainly of iodine-induced acne. Contraindications for the use of iodine are all states of subclinical or overt hyperthyroidism, thyroid autoimmune diseases and the rare dermatological disease Dermatitis herpetiformis Duhring. 

Abbreviations-. oHTA, overt hyperthyroidism in thyroid autonomy scHTA, subclinical hyperthyroidism in thyroid autonomy oHGD, overt hyperthyroidism in Graves disease scGD, subclinical hyperthyroidism in Graves disease MRR, maximum relative risk Inc, incidence RR, relative risk. 

Overt hyperthyroidism is defined by suppression of TSH and elevation of free thyroxine and T3. Subclinical hyperthyroidism is defined by suppression of TSH, but normal values of free thyroxine and T3. 

Incidence of Overt Hyperthyroidism after Iodine Fortification of Sait... 

The registry has enabled us to prospectively follow the incidence of overt hyperthyroidism in the two population cohorts after IF of salt. At baseline, the crude incidence rate of hyperthyroidism (without follow-up verification of diagnosis in individual patients) in the entire Aalborg -F Copenhagen cohort was 102.8/100000/year. The incidence rate increased during IF, but became stable at a level about 35% above baseline (Pedersen et al., 2006). 

Figure 119.5 Incidence rates of overt hyperthyroidism before and after iodine fortification (IF) of salt. The incidence rate of hyperthyroidism in Aalborg (moderate ID) and Copenhagen (mild ID) before and after the first 6 years of IF of salt. Basic is the time before IF of salt (1997-1998), 1999-2000 is the period of voluntary IF, 2001-2002 is the early, and 2003-2004 is the late period of mandatory IF. The incidence of hyperthyroidism increased significantly in both subcohorts during the study period. In Aalborg, the increase was more pronounced and came before the increase in Copenhagen. Aalborg baseline vs. voluntary IF, P< 0.001 voluntary IF vs. early mandatory IF, P s 0.001 early vs. late mandatory IF, ns. Copenhagen baseline vs. voluntary IF, ns voluntary IF vs. early mandatory IF, P s 0.001 early vs. late mandatory IF, ns. Statistical significance compared with baseline, P < 0.05 P s 0.01 P s 0.001. Data from Pedersen et al., (2006).

No significant difference in the cumulative incidence of overt hyperthyroidism was observed between MDI, MAI and El areas. Iodine supplementation in a mildly deficient iodine population might not increase the incidence of overt hyperthyroidism. 

Our findings showed that iodine supplementation to areas with MDI did not cause an increase in the incidence of overt hyperthyroidism and GD. In 2002, Lauberg reported that after supplementing iodine to areas with... 

Figure 125.3 The relationship between urinary iodine levels and the prevalence of overt hyperthyroidism in GD family members. MUI median urinary iodine excretion GD, Graves disease 234 family members urinary samples were taken and 69 of them were diagnosed with overt hyperthyroidism. The incidence of overt hyperthyroidism in groups with urinary iodine between 500 and 599 (ig/l were significantly higher than those with urinary iodine 100 99(jg/l (P < 0.05).

Iodine Excess Promoted the Development of Overt Hyperthyroidism in GD Famiiy Members... 

Thyrotoxicosis is a type of very late adverse reaction seen after iodine-based contrast media. Untreated Graves disease and multinodular goiter and thyroid autonomy are risks for this adverse reaction. Patients with hyperthyroidism are usually advised not to have iodinated contrast media injection. Patients with normal thyroid function are thought to be at low risk for this condition [3 ]. There are few studies that assess the relationship between iodinated contrast media exposure and thyroid function disorders. In a nested case-control study of 4096 patient intervals, iodinated contrast exposure was associated with incident hyperthyroidism (odds ratio or OR = 1.98 95% confidence interval or Cl = 1.08-3.60) but not statistically significantly associated with incident hypothyroidism (OR = 1.58 95% Cl, 0.95-2.62). Also, incident overt hyperthyroidism (follow-up thyrotropin levelsO.l mlU/L OR, 2.50 95% Cl, 1.06-5.93) and incident overt hypothyroidism (follow-up thyrotropin level >10 mlU/L OR, 3.05 95% C3,1.07-8.72) were found to be associated with iodinated contrast media exposxue [4 ]. 

---