Hypertrichosis due to Congenital Hypothyroidism.

Sir,

A 7-month-old male infant was referred to our hospital for evaluation of excessive hair on forehead. He was born after full-term gestation by normal vaginal delivery from nonconsanguineous parents. His birth weight was 2.8 kg. The family history revealed no thyroid disease. Baby had passed meconium on the second day of life. History of prolonged jaundice was present in the neonatal period. On enquiry, there was also history of hoarse cry, excessive sleepiness, constipation, and poor feeding. The present weight of the baby was 4.1 kg suggestive of failure to thrive. There was excessive hair on forehead, a large tongue, distended abdomen, left inguinal hernia, and umbilical hernia [Figure 1]. His thyroid hormone studies revealed thyroxin (FT4) 0.4 ng/dl (normal 0.9–2.6), FT3 110 pg/dl (normal 240–560), TSH (thyroid-stimulating hormone) >75 mIu/ml (normal 0.7–6.4), and thyroglobulin 5.8 ng/ml (normal 10.6–92). Thyroid ultrasound showed small thyroid gland with right lobe 5×5×6 mm and left lobe 4.5×5.5×4 mm with apparent homogenous echo pattern without focal lesions. Technetium 99 thyroid scan revealed thyroid gland almost none visualized, no evidence of functioning ectopic thyroid tissue in the neck. Thyroid autoantibodies could not be done due to financial constraints. A final diagnosis of hypertrichosis secondary to congenital hypothyroidism was made and levothyroxine was started (4 μg/kg/day). Thyroid hormone studies were done regularly and titration of levothyroxine dose was done. On follow-up after 4 months, the patient showed marked improvement in the symptoms with disappearance of his excessive hair.

Figure 1

Clinical photo showing excessive hair on forehead, a large tongue, distended abdomen, left inguinal hernia, and umbilical hernia

Congenital hypothyroidism is the most common congenital endocrine disorder and occurs at rate of 1 in 3000–4000 births.[1] The causes can be divided into two groups: thyroid developmental defects (thyroid dysgenesis) and inborn errors of thyroid hormone biosynthesis (dyshormonogenesis). As few signs or symptoms are present in the neonatal period, routine screening is the only means of detection. Hypertrichosis is defined as an excessive growth of hair (terminal, vellus, or lanugo) in areas of the body that are not predominantly androgen-dependent.[2] Hypothyroidism is usually associated with loss of hair. Very few cases of hypertrichosis associated with congenital hypothyroidism have been described.[3-5] The causal association between hypothyroidism and hypertrichosis has not been reported in neonatal period, although congenitally hypothyroid infants often have a low hairline. Perloff reported four cases of hirsutism in children, who responded to thyroxine replacement therapy.[3] A 10-year-old girl with hypertrichosis associated with primary hypothyroidism that resolved by thyroxine therapy has also been described.[4] Nishi et al. reported three children with untreated primary hypothyroidism resulting in pituitary hyperplasia and hypertrichosis.[5] These abnormalities disappeared after thyroid hormone therapy. In our patient, stimulation of the growth of hair via adrenal androgens by TSH may be the probable pathophysiological mechanism. We could not do further hormonal studies due to financial constraints. However, the fact that the hypertrichosis resolved after 4 months’ replacement treatment with thyroxine establishes the causal relationship between hypertrichosis and hypothyroidism.

In conclusion, we suggest that full assessment of thyroid function be carried out in all cases of hypertrichosis or abnormal distribution of body hair.