Nail Changes Associated With Thyroid Disease
Nail changes with thyroid disease have not been well studied. Nail findings are helpful in early diagnosis of thyroid disorders and therefore are important for dermatologist education. We reviewed the literature on nail changes in thyroid patients and found that onycholysis and slow-growing, thin nails are associated with hypothyroidism and that onycholysis, koilonychia, and brittle nails changes are associated with hyperthyroidism.
Practice Points
- Koilonychia is associated with hyperthyroidism.
- Clubbing is a manifestation of thyroid acropachy in Graves disease and also affects other patients with hyperthyroidism.
- Onycholysis improves in patients with hypothyroidism treated with thyroid hormone replacement therapy.
Comment
There are limited data describing nail changes with thyroid disease. Singal and Arora3 reported in their clinical review of nail changes in systemic disease that koilonychia, onycholysis, and melanonychia are associated with thyroid disorders. We similarly found that koilonychia and onycholysis are associated with thyroid disorders without an association with melanonychia.
In his clinical review of thyroid hormone action on the skin, Safer12 described hypothyroid patients having coarse, dull, thin, and brittle nails, whereas in thyrotoxicosis, patients had shiny, soft, and concave nails with onycholysis; however, the author commented that there were limited data on the clinical findings in thyroid disorders. These nail findings are consistent with our results, but onycholysis was more common in hypothyroid patients than in hyperthyroid patients in our review. Fox13 reported on 30 cases of onycholysis, stating that it affected patients with hypothyroidism and improved with thyroid treatment. In a clinical review of 8 commonly seen nail abnormalities, Fowler et al14 reported that hyperthyroidism was associated with nail findings in 5% of cases and may result in onycholysis of the fourth and fifth nails or all nails. They also reported that onychorrhexis may be seen in patients with hypothyroidism, a finding that differed from our results.14
The mechanism of nail changes in thyroid disease has not been well studied. A protein/amino acid–deficiency state may contribute to the development of koilonychia. Hyperthyroid patients, who have high metabolic activity, may have hypoalbuminemia, leading to koilonychia.15 Hypothyroidism causes hypothermia from decreased metabolic rate and secondary compensatory vasoconstriction. Vasoconstriction decreases blood flow of nutrients and oxygen to cutaneous structures and may cause slow-growing, brittle nails. In hyperthyroidism, vasodilation alternatively may contribute to the fast-growing nails. Anti–thyroid-stimulating hormone receptor antibodies in Graves disease may increase the synthesis of hyaluronic acid and glycosaminoglycans from fibroblasts, keratinocytes, adipocytes, or endothelial cells in the dermis and may contribute to development of clubbing.16
Our review is subject to several limitations. We recorded nail findings as they were described in the original studies; however, we could not confirm the accuracy of these descriptions. In addition, some specific nail changes were not described in sufficient detail. In all but 1 study, dermatologists performed the physical examination. In the study by Al-Dabbagh and Al-Abachi,10 the physical examinations were performed by general medicine physicians, but they selected only for patients with koilonychia and did not assess for other skin findings. Fragile nails and brittle nails were described in hypothyroid and hyperthyroid patients, but these nail changes were not described in detail. There also were studies describing nail changes in thyroid patients; some studies had small numbers of patients, and many did not have a control group.
Conclusion
Nail changes may be early clinical presenting signs of thyroid disorders and may be the clue to prompt diagnosis of thyroid disease. Dermatologists should be mindful that fragile, slow-growing, thin nails and onycholysis are associated with hypothyroidism and that koilonychia, softening, onycholysis, and brittle nail changes may be seen in hyperthyroidism. Our review aimed to describe nail changes associated with thyroid disease to guide dermatologists on diagnosis and promote future research on dermatologic manifestations of thyroid disease. Future research is necessary to explore the association between koilonychia and hyperthyroidism as well as the association of nail changes with thyroid disease duration and severity.
